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148 Cards in this Set
- Front
- Back
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Define the term 'Allele' [1 mark]
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One of the different forms of a gene
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What is a gene? [1 mark]
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A section of DNA on a chromosome, which codes for specific polypeptide.
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State the characteristics of the genetic code [3-5 marks]
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Triploid
Degenerate 'Start' 'stop' codons Universal code No overlapping |
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What does 'triplet code' mean, and why is it needed? [3-4 marks]
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Codons made up of three bases
As there are only 4 bases, but 21 amino acids, if codons were made up of only 2 bases, there would be 16 possibilities (too few) A triplet code gives 64 possibilities, (more than enough) |
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What does the term 'degenerate code' mean?
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Most amino acids have more then one triplet code.
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Explain what it means when the genetic code is described as 'universal' and 'non-overlapping'. [2 marks]
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Universal meaning that code is exactly the same for all living organisms
Non-overlapping meaning codons read separately |
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What is 'semi-conservative replication' [1 mark]
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Each new DNA molecule made up of: one 'original' template strand and one new strand
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How does DNA undergo replication? [3 mark]
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-Hydrogen bonds break (DNA helicase), strands separate, DNA molecule 'unzips'
-DNA polymerase catalyses addition of free nucleotides to exposed bases. -Each chain acts as 'template', for newly synthesised strand [semi-conservative replication hypothesis] |
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Out line the basic process of protein synthesis. [ 2-4 marks]
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1-DNA does not leave nucleus, but acts as template for production of mRNA (transcription), forming sequences of instructions.
2-mRNA acts as template to which complementary tRNA molecules attach; the amino acids they carry form peptide bonds, so polypeptide chain formed |
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Describe how 'Transcription' occurs, in 3 main points?
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DNA helicase, acts on specific region of DNA (cistron), breaking H bonds, causes 2 stands to separate exposing nucleotide bases in that region
RNA polymerase links to template strand, free nucleotides align opposite template strand, (complementary) RNA polymerase moves along DNA, synthesising a strand of mRNA, which can carry instructions out of nucleus |
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Describe how 'translation' occurs, in 5 main points: (including what occurs to the ribosome, the tRNA molecules, the mRNA strand, and amino acids)
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Ribosome attaches to end of mRNA strand;
tRNA with complementary anticodon to first mRNA codon, attaches to ribosome; Second tRNA with complementary anticodon to second mRNA codon attaches to other attachment site. Amino acids (attached to tRNA) are close enough to form peptide bond. First tRNA leaves first attachment site, ribosome moves one codon along mRNA strand, leaving an attachment site vacant. As ribosome moves along mRNA one site at a time, the tRNA with appropriate anti codon fills vacant slots, and amino acids form peptide bond with last member of chain. Continues until 'stop' codon reached |
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State the roles of:
1) mRNA 2) tRNA 3) rRNA [3 marks] |
1) mRNA: carries instructions out of nucleus, acts as template for tRNA
2)tRNA: attach to ribosome on mRNA, bring amino acids together 3)rRNA: makes up the ribosomes |
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A sequence of bases on the template strand of DNA is:
CCA GAG CAT TTC [2 marks] 1) What is the sequence of bases on the mRNA molecule? 2) What is the sequence of bases forming the anticodons of the tRNA molecules? |
1)mRNA: GGU CUC GUA AAG
2)tRNA: CCA GAG CAU UUC |
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State and describe the different levels of protein structure [4 marks]
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Primary structure: sequence of amino acids in polypeptide chain
Secondary structure: The coiling/ folding of the polypeptide chain. Tertiary structure: the 3D structure and shape of the polypeptide chain. Quaternary structure: The protein formed from the interaction/ combination of different polypeptide chains |
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What happens to the tRNA when it is released from its specific amino acid? [2 marks]
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Recycled back into the amino acid pool
Collects another amino acid (the same specific amino acids as before) Energy, from ATP, used for attachment (called activation) |
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Differences between DNA and RNA? [3 marks]
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DNA / RNA
De-oxy-ribose sugar/ Ribose sugar Double stranded/ Single stranded Adanine+Thyamine/Adanine +URACILL |
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Differences between Meiosis I and Mitosis [6 marks]
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Mitosis:
Single chromosome No crossing over 1 chromatid each side of equator No random assortment Division of centromere Chromosome number stays the same Meiosis I: Double, (homologous) chromosome pairs Crossing over at chiasmatta Whole chromosomes either side of equator Random assortment No division of centromeres At tellophase, chromosome number is halved |
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What is the difference between Haploid and Diploid [2 marks]
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Haploid (N); only one set of chromosomes, as in gametes
Diploid (2N); two sets of chromosomes; as in normal somatic cells |
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What does the term 'homolgous' mean? [1 mark]
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A pair of chromosomes, one inherited from each parent, that have corresponding gene sequences (but different alleles) and that pair during meiosis.
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State and describe the process of Meiosis 1 and 2 [up to 8 marks, possible essay Q]
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PROPHASE 1: Homologous chromosomes pair up forming bivalents, crossing over of chromosome pairs occurs, forming chiasmatta, where genetic material may be exchanged.
METAPHASE 1: chromosome line up on equator, independent assortment ANAPHASE 1: Chromosome spate TELOPHASE 1: membranes reform, two cells producd PROPHASE 2: No crossing over, new spindly reforms at 90* to previous division. METAPHASE 2: chromatids line up on equator ANAPHASE 2: chromatids pulled apart TELLOPHASE: 4, non identical, haploid cells produced |
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What is the significance of meiosis? [3 marks]
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Meioson create division in three ways:
1- Random fertilisation of gametes, (creating different combinations of chromosomes) 2- Independent/ random assortment of chromosomes on equator daring's metaphase 1 3- Crossing over during chiasmatta formation, during prophase 1, allows exchange of genetic material |
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Name key parts of female reproductive system, and name functions
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Ovary: eggs formed through oogenesis
Fallopian tube/oviduct: fertilisation occurs as ova travels down tube Uterus: Has muscular walls, well supplied with blood, where the embryo will implant during pregnancy, endometrium lining shed during mensuration Cervix: Allows flow of menstrual blood from the uterus into the vagina, and direct the sperms into the uterus during intercourse. Vagina: Where willy goes and sperm is deposited |
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Name the key parts of male reproductive system and describe functions.
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Seminal Vesicle: (produces secretion, aids sperm mobility)
Prostate gland: (produces alkaline solution, neutralises acidity of urine, in urethra) Vas deferens: Tube connecting testis to urethra Seminiferous tubules: produced spermatozoa Epididymis: spermatozoa stored. |
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What is gametogenesis? [2 marks]
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The production of gametes in the sex cells:
Spermatogenesis: Production of sperm in testis Oogenesis: Production of eggs/ova in ovary |
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State where Spermatogenisis takes place and describe the process.
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Takes place in seminiferous tubules-Formed from germinal epithelium cells
Spermatogenia (2N) undergo mitosis form primary spermocytes (2N) Spermocytes undergo first meiotic division to form secondary spermocytes (N) Secondary spermocytes undergo the 2nd meiotic division to form spermatids which differentiate into spermatozoa. SO: Spermatogenia >(mitosis)>Spermocytes >(1st meiotic division) > Secondary Spermocytes> (2nd meiotic division)> Spermatid> (differentiation)> spermatozoa |
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What is the function of serotoli cells? [2 marks]
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Nourishment and protection of spermatozoa
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Describe the process of oogenesis
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Oogenia (formed before birth) undergo mitosis forming primary oocyte.
Germinal epithelial cells divide to form follicle cells which surround the primary oocyte to create primary follicles Primary ooctyes do not mature untill just before ovulation when several follicles start to develop;only one matures into graffian follicle. The primary oocyte then completes 1st meiotic division to form small polar body and secondary oocyte (N) released in ovulation. Secondary oocyte begins meiotic division but halts at metaphase until fertilisation. |
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What happens to the corpus luteum, when fertalisation occurs and when fertalisation does not occur.
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(The corpus luteum is what is formed from the graffian follicle after it releases secondary oocyte)
If fertalisation occurs it releses pregnancy hormones (oestrogen and progesterone) which supress FSH and LH production, preventing further ovulation and maintaining the thickness of the endometrium wall; so pregnancy maintained. If pregnancy does not occur, then it will degenerate |
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Explain the advantages of internal fertilisation?
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An adaption to life on land
Organisms can become independent of water, as sperm introduced directly into female reproductive tract. |
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Desribe fertalisation and the events that follow.
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When sperm reaches the zona pelucida jelly layer of secondary oocyte, its acrosome membrane bursts, releasing enzymes which digest the jelly layer.
The inversion on the enzymes causes needle like filament to form, piercing through layer, male nucleus travels down tube. Causes fertilisation membrane to form, so no further sperm can get through. Also stimulates oocytes second meiotic division, forming ovum. Nuclei of sperm and ovum fuse to form diploid nucleus (2N) |
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State similarities between the transfer of the male nucleus to the ovum and the equivalent process of fertilisation in plant reproduction [3 marks]
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Both positively chemotrophic
Both use enzymes to digest pathway Both have tubes which nucleus travels through, Both of there membranes burst, to release the male nucleus |
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What is implanation [2 marks]
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After fertilisation, zygote develops to from hollow ball of cells (blastocyst)
After 3 days blastocyst reach uterus and embeds in endometrium wall > this is implantation. |
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What is 'Subfertility' in comparison to 'Infertility'
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Subfertility is the difficulty in conceiving naturally (reasons may affect male, female, or both partners)
Infertility is the complete inability to conceive a child, very rare |
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What are the two main causes of female infertility?
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1) Failure to ovulate, associated with absent/ irregular menstrual cycle
2) Blockage of fallopian tubes preventing passage of ovum to site of fertilisation in fallopian tubes. (Blockage may be caused by infection) |
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What does the term 'monoclonal anti bodies' mean?
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Many copies of one type of anti-body
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What is an antigen?
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A non-self protein, that is recognised by immune system, brings about an immune response.
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Explain how a pregnancy testing kit works
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Pregnancy testing kits rely on the reaction between antibodies bound to coloured beads and a hormone in urine. (HGC)- the antigen
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What is 'Invitro fertilisation, (IVF), and describe the technique
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Fertilisation takes place out side the body, zygote implanted into uterous
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Name the parts of the:
1) The carpel (female plant reproductive structures) 2)The Stamen (male plant reproductive structures) |
Carpel: stigma, style, ovary
Stamen: anther and fillament |
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Where in the plant does meiosis take place to produce male and female gamets
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Meiosis takes place in anther (to make pollen) and in ovary to make embryo sac/ ovule
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What is pollination [1 mar]
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Transfer of pollen to stigma
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The genetic implications for:
1) self-pollination 2)Cross-pollination |
Self pollination; pollen transported to the stigma of the same flower, or another flower on same plant- leads to self- fertilisation-so depends on random assortment and crossing over for variation, so less genetic variation.
Cross pollination leads to cross fertilisation, so more variation. |
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Describe four differences between wind pollinated and insect pollinated flowers. [4 marks]
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Insect pollinated vs. wind pollinated
Colourful petals, /small inconspicuous petals Anther inside flower/ anthers hang outside flower Stigma within flower/ Stigma large feathery less, sticky, pollen/ more, smaller, lighter pollen |
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Describe the structure of the male gamet in plants
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Sculptured exine wall, (resistant to desiccation)
Inner wall A generative nucleus; later gives rise to 2 male nuclei Pollen tube nucleus |
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Describe the development of the female plant gamete
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Ovules produced inside ovary, the female gametes (egg nucleus) develops inside ovule)
The ovule undergoes meiosis, producing a haploid embryo sac; Within the embryo sac: there are the egg cell nucleus and the polar nuclei. |
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What happens after male pollen grain lands on female stigma?
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If compatible, stigma produces sugary solution, makes pollen grain germinate (producing a pollen tube)
Pollen tube grows down style, secretes enzymes digests its way through tissue, gaining nutrients from digested products Pollen tube nuclei at tip of tube, controls growth - male nuclei follow behind -pollen tube grows through integuments (microphyle), passes into embryo sac, membrane bursts and male nuclei released. -1 male nucleus fuses with female nucleas (forming zygote) -1 male nucleus fuses with polar nucleiforming triploid endosperm |
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Which parts develop into the:
1) Embryo (with plumule and radical) 2) Food store 3) Seed coat/ test 4) The Seed 5) The fruit |
1) Zygote becomes the embryo
2) The triploid endosperm(formed from polar nuclei) becomes food source 3) The integuments becomes the seed coat 4) Ovule become seed 5) Ovary becomes fruit |
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State Mendel's first law?[2 marks]
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Characteristics of an organism are coded for pair pairs of factors (alleles)
Gametes contain only one allele (factor) |
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State Mendel's second law; [1 mark]
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Each member of an allelic pair may combine randomly with another
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Define the term 'dominant allele'. [1 mark]
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Expresses itself in both heterozygous and homozygous condition; always show in phenotype
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Explain the term 'sex linked ressesive allele' [4 marks]
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Carried on the sex chromosome (X)
Only expresses itself if both chromosomes carry the allele in females (homozygous condition) Will always be expressed in males (as y is not homolgous) An Allele is a different form of the same gene |
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What is meant by a 'gene mutation'? [1 mark]
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Change in the base pairs on a gene [NOT DNA]
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What would the effect of a gene mutation be on the protein? [3 marks]
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Change in amino acid order
So protein changes shape Thus a non-functional protein in created |
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What does 'non-disjunction' mean?
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The failure of homologous pairs to separate normally during nuclear division
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What is a Meristem?
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a region of plant tissue (i.e. growing roots/ shoots) consisting of actively dividing cells forming new tissues
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Why can't an organism with an odd number of chromosomes reproduce? [3 marks]
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pairing of homologous chromosomes cannot take place
No meiosis So no haploid gametes produced |
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What are major conerns with genetically modified crops? (and the use of virus's/ bacteria as vectors for genes) [5 marks]
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Reversion of virus to disease causing form
Virus/bacteria could be harmful to humans Could transfer to another species Unknown future side effects (An ethical reason: eg only for superficial purposes, no nutritional purpose) |
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What is it called when male and female gametes fuse?
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Fertilisation baby ;) Gigidy..
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How would a cell make sure the genetic code is read in the correct direction during protein synthesis? [1 mark]
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As it is a degenerate code, their is a 'start' codon which does not code for an amino acid
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Proflavin is a chemical which alters the base sequence of DNA.
What is the name for such a change? [1 mark] |
Mutation
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What is the effect of the deletion ( a type of gene mutation) of the first base in the DNA sequence? [2 marks]
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This would cause a change in the position of each codon
So there would be a different sequence of amino acids, and a different Polypeptide would be produced |
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Explain how variation occurs as a result of gene mutation [2 marks]
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A change in the base sequence of a gene
resulting in the alteration of a protein/ or creation of a non functional protein |
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State two causes of variation [2 marks]
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Radiation
Carcinogens Non-disjunction |
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Explain why variations caused by mutation can be important to the survival of a species? [2 marks]
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A mutation increases the amount of variation on the gene pool for natural selection
could provide a selective advantage |
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Give the main advantage of crossing over of homologous chromosomes during prophase 1 of meiosis [1 mark]
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Increased genetic variation
Allows evolution by natural selection |
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What are the functions of these parts of a flower: [4 marks]
a) anther b) stigma c) sepal d) peta; |
a) Anther > where pollen grains are produced
b) Stigma> receptive surface for pollen c) Sepal> encloses and protects the flower in the bud. d) Petals> Attracts insects for pollination |
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What exactly is the 'Ovule' in a plant?
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The ovule consists of: the outer integuments surrounding an embryo sac, inside which is contained the nuclei
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In terms of seed germination, what exactly is dormancy? [1 mark]
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A period when active growth is suspended, germination occurs when specific conditions are met
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What are the conditions for successful germination? [3 marks]
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A suitable temp: the optimum temp for germination will be the optimum for the enzymes involves in germination. (This varies from species to species)
Water: for mobilisation of hydrolytic enzymes, rehydration of dry tissues, and helps crack seed coat. Oxygen: respiration makes energy, in the form of ATP, which is needed for metabolism and growth. |
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Describe how the pollen tube grows [4 marks]
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(chemotropic process)
Controlled by pollen tube nucleus Secretes/ releases enzymes digests its pathway down style, absorbs digested products for growth |
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How might the fruit of a plant may be advantageous for survival of species [2]
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Animals eat fruit, lead to dispersal of seeds, avoid competition with parent plant and reduced over crowding.
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Describe the changes in dry mass in seeds during germination [4 mark]
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The food reserves of the endosperm are broken down by hydrolysis; converted from starch to maltose by amylase enzyme
the soluble sugars pass to embryo; when first leaves produced, photosynthesis occurs, resulting in increase in biomass of seedling. |
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How are the food reserves in endosperm of seed utilised?
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Hydrolysed by enzyme amylase; broken down from starch to maltose which is a soluble sugar and can be transported to embryo.
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The term describing th genetic make up of an organism and describes all the alleles an organism contains:
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Genotype
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Three main characteristics of genes:
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They can separate and combine
The can mutate They code for the production of specific polypeptides |
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The type of inheritance involving a single characteristic (e.g. colour), Concerns the inheritance of two alleles involving a single gene
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Monohybring cross
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How would you determine whether a particular dominant characteristic observed is in a homozygous or heterozygous condition?
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Backcross:
Crossing the animal with a known recessive genotype. If the resulting offspring ALL show the dominant characteristic you know it is homozygous dominant If the offspring include some with recessive characteristics then the animal must be heterozygous. |
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WHat is the term for inheritance involving two separate genes:
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Dyhybrid inheritance
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What are the observable characteristics of an organism called [1]
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The phenotype
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What is the term for the position occupied on an allele by a gene [1]
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Locus
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Give the formula for the chi squared test:
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(Observed value - Expected Value)²
Expected value |
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What is 'the degree of freedom' in terms of statistical tests?
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For chi squared, the degree of freedom is:
One less than the number of classes of data e.g. for a dyhybrid cross this would be 4-1=3df |
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What is it called when a heterozygous individual has a phenotype which is an intermediate of its homozygous parents?
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Co-dominance
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What is the difference between X and Y chromosomes?
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The X chromosome is much longer than the Y chromosome, this means the Y chromosome does not have an equivalent portion; and thus cannot carry alleles.
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What is a carrier?
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An individual with one normal allele and one potential harmful recessive allele
The individual is phenotypically normal |
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What is 'linkage'
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linkage occurs when two different genes are found on the same chromosome, so at fertilisation the linked genes pass into offspring together
UNLESS crossing over occured |
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What is a chromosomal mutation?
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A change in number or structure of chromosomes
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What is polyploidy?
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An increase in a complete set of chromosomes, triploids are usually sterile as they cannot form homologous pairs
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When are chromosomal mutations most likely to occur?
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During meiosis, when chromosomes line up on equator and are separate during anaphase. May lead to chromosomes not being shared equally between daughter cells
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What exactly is a selective advantage?
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A characteristic of an organism that enables it to surive and reproduce better than other organisms in a population in a given environment
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What is an Onconogene?
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A mutated gene that causes cancer
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What are 'Mutagens'? Give some examples?
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Factors which increase chances of mutations occurring:
X-rays, gamma radiation and UV light, chemicals such as polycyclic hydrocarbons (in cigarette smoke) |
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What do you call an agent that causes cancer?
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A carcinogen
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How exactly do carcinogens work?
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Affect the DNA in cells, resulting in mutations affecting regulation of cell division.
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Two types of genetic (Heritable) variation [2]
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Continuous variation
Discontinuous variation |
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Continues variation [3]
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When a characteristic is controlled by a number of genes and the difference in characteristics is not clear cut.
E.g. height; if an individual has inherited a number of alleles for tallness from perants, that individual had potential to grow tall, however growth also depends on environment/ nutrition ect |
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Discontinues Variation [2]
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Characteristics which are clear cut, easy to tell apart; controlled by a single gene.
E.g. ABO blood grouping system |
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Varriation can be due to...?
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A combination of genetic and environmental differences
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Which is which when it comes to InTRA specific competition and inTER specific completion?
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IntRA specific competition is completion between individuals of the same species
InTER specific completion is completion between different species |
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What is a Selection pressure?
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The environmental force influencing to frequency of alleles in a population
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Variation due to characters controlled by single gene
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Discontinues variation
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Population [2]
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A group of interbreeding individuals of the same species, occupying the same habitat at the same time
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Gene pool
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the total number of alleles in a population at any one time
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Allele frequancy
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the number of times an allele occrs within the gene pool
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Genetic drift
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Chance variations in allele frequencies in a population
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A population is?
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A group of interbreeding individuals of the same species, occupying the same habitat at the same time
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The hardy-Weinberg equation can be used to..?
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Calculate the allele frequency of a defective allele causing a genetic disorder (such as cystic fibrosis) in the gene pool of the human population
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Natural selection:
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a process which ecorages the transmission of favourable genes, and hinders the transmission of unfavourable ones
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The principles of Darwin's theory of evolution? [4-5]
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-Darwin suggested there is variation within species.
-All species overproduce in terms of offspring, yet numbers remain constant- so struggle for survival. -Those who have beneficial characteristic survive (survival of the fittest) -This eventually leads to a change to the frequency of alleles in a gene pool, due to repetition generation after generation |
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What is adaptive radiation
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Species become adapted to fulfil different envriometal niches, eventualy forming new species.
Example: the gallapagos finches, adapted different beak sizes depending on what they ate (insects/ seeds/ nuts/ fruits) |
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Describe ways which can be used to tell the relationship of different species? And even can be used to support theory of evolution
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Fossil records: eg pentadactyl limb
DNA hybridisation: comparing base sequence Comparison of morphology Compare amino-acid order of proteins. |
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Define the term 'species'
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A group of similar individuals, able to interbreed and produce fertile offspring; and is reproductively isolated from other such groups
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What are 'reproductive isolation mechanisms'???
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Any factor preventing individuals mating to produce fertile offspring
geographical features Habitatt changes behavioural mechanisms morphology breeding mechanisms |
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Allopatric speciation is....?
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Where two populations start to diverge and develop mechanisms which cause them to become reproductively isololated from on another
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Sympatric speciation
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when oranisms inhabitying the same area become reproductively islolated into two groups, when there are no physical barriers
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What exactly is a 'cone'?
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A group if genetically identical organisms, formed from a single parent, as a result of asexual reproduction, or by artificial means.
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Advantages of mammalian cloning?
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Enables desirable characteristics to be preserved for future generations
Allows many genetically identical copies of animals to be produces (useful for farming) Cell culture can be used for production of cells in quantity, for medical research and for monoclonal antibodies |
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Disadvantages of mammalian cloning?
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Very expensive and unreliable
Inadvertant selection of undesirable/ disadvantageous alleles May show unforeseen long term effects; such as premature aging |
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Tissue culture is..?
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The technique of growing cells in a lab
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What are stem cells?
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Undifferentiated cells, capable of dividing to give rise to cells which can develop into different types of specialised cells
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Applications of tissue engineering? [4]
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Treatment of burns/scars
Blood vesel treatment Bone and cartalige repair Treatment of degernerative nerve disease |
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Give some sources of stem cells [2]
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Early embryos or adult bone marrow
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Reasons for the use of stem cells [3]
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Huge benefits; cells could be used to treat range of illness
Supply of embryos comes from surplus which not used in fertility treatment, so had no potential to develop Human embryos not they only source of stem cells also bone marrow |
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Argumnts against stem cell use? [3]
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Could be considered unacceptable to use embryos in this way as a source of potential life
Could be seen as thin end of wedge; could lead to reproductive cloning, fundamentally devaluing human life Research could be used for human cloning in other countrys |
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Micrpropogation?
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A cost effective way of producing large numbers of genetically identicall plants, which are clones of a single parent
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What a totipotent cells?
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Cells which can mature into a body cell
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Describe processs of micrpropogation [7]
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Plant with desired characteristics selected.
Sterile scalpel removed meristem from shoot |
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What is meant by 'resistance'? [1]
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The ability of an organism, to survive a dose of poison that would normally be lethal to it.
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Describe how resistance can build up in a population [5-6]
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Resistance arises from mutations arising randomly in population (such as rats/ bacteria)
Gives those organisms a selective advantage: When poison used there is a Selective pressure, favouring resistant types, as those that are not resistant are killed. So resistant organisms survive and pass on genes to offspring; Leading to an increase in the resistant alleles in gene pool of population (The greater quantity/frequency of poisons use, greater selection pressure) |
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Give an example of how a bacterium may be resistant to a anti-biotic [1]
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Ability of bacterium to produce an enzyme which breaks down the antibiotic
e.g. Some bacteria produce penicillinase ; this renders penicillin ineffective |
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Why is the problem of resistance worse in bacteria, than other organisms (such as rats)? [2]
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Bacte
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Explain the link between resistance to Warfarin in rats, and diet? [4]
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Resistance controlled by a dominant allele (R) at a single locus; However this gene also confers a requirement for vitamin K.
Homozygotes (rr) killed by warfarin Homozygotes (RR) resistant but have massive requirement for vitamin K; difficult to meet Heterozygotes (Rr) resistant and low vitamin K requirement (heterozygote advantage) |
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What is meant by a 'heterozygote advantage'? [2]
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Heterozygotes favoured in selection; so both alleles (R and r) will be maintained in population.
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Artificial selection? [3]
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Carried out by humans to obtain plants/animals with characteristics humans require
May take years to develop organisms with required characteristics Produces organisms belonging to same species; described as breeds or varieties. |
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Explain disadvantages of inbreeding in artificial selection? [3]
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Promotes homozygosity
Increases chances of harmful recessive genes expressing themselves, as greater risk of double recessive occurring Leads to loss of vigour, size and fertility (inbreeding depression) ; so out breeding required to introduce new genes |
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What are the advantages of out breeding [3]
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Promote heterozygosity
Introduces hybrid vigour; where organisms grow more strongly, this arises when new sets of chromosomes are complementary |
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What is biodiversity? [1]
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The variety of life in the world or in a particular habitat or ecosystem.
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What is extinction? [2]
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The loss of species.
A natural process has been taken place since life first evolves; it is the current rate of extinction which underlies the biodiversity crisis |
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Examples of endangered animals?
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Mountain Gorillas
Giant Pandas Tigers Polar Bears |
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Three main causes for species becoming endangered of extinct? [3]
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Loss of habitat: (deforestation/ pollution drainage of wetlands)
Overhunting by humans Competition from introduced species (e.g. red squirrel) |
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Discuss arguments for and against the screening of apparently normal individuals for genetic disorders [5]
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Would allow identification of those at risk of developing illness such as cancer
Which would affect a persons life style choices Means those at high risk could be more aware; so more likely to have early diagnosis and treatment Could lead to discrimination; i.e. by employers/ insurance companies Questions over who owns information |
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The process which arranges the correct sequence of amino acids in a polypeptide [1]
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translation
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What ensures the correct amino acid is adds to the polypeptide during translation? [3]
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The codons on the mRNA copied from DNA nucleic code
mRNA codons complementary to anti codon on tRNA; so codons and anti codons match up. Each tRNA links to a specific amino acid |
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Suggest two ways chromosomal DNA fragments can be obtained (ie for genetic engineering) [3]
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Reverse transcriptase; mRNA section converted into DNA fragment using DNA polymerase
Restriction enzymes; cut DNA fragments straight from DNA (leaves sticky ends) |
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Conserns of gm crops [5]
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Reversion of the virus (uses as vector) to disease causing form
Could be toxic to humans Unforeseen long term side effects of eating GM crops Only useful if nutritional value Increase cost, pressure on farmers |
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What are the two major components of a virus? [2]
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Nucleic acid (DNA)
Protein |
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In gene therapy, after the replacement gene is inside the cell, what must happen for successful treatment? [5]
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Gets into nucleus
Insertion into genome/chromosome Transcription (mRNA instructions copied) Translation (mRNA acts as template for tRNA, to make the polypeptide Functioning protein created. |
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Two way population in rat population can spread [2]
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Reproduction/ interbreeding
Migration |
