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64 Cards in this Set

  • Front
  • Back
gene
basic unit of heredity
genotype
genetic makeup
phenotype
physical manifestation due to specific genetic makeup
allele
alternative versions of a gene when multiple versions exist
true-breeding individuals
individuals that when self-crossed produce progeny with only the same parental phenotypes
Mendel
studied the garden pea. crossed pure breeds with different traits and mated them to statistically analyze the inheritance of the traits in the progeny.
mendel's first law
law of segregation; means that when two alleles separate during meiosis, gametes carry only one version of the gene; it can be maternal or paternal. gametes can end up with different combinations of maternal or paternal alleles for each gene
for each heritable trait, organisms have ____ alleles.
two; one paternal and one maternal.
Mendel's Law of Dominance
when an organism is heterozygous in genotype, the dominant of the two alleles for that gene is exhibited in the phenotype.
monohybrid cross
a cross in which only one trait is studied.
P=
F=
parental generation
filial generation
punnett square
P P
p Pp Pp

p Pp Pp
dihybrid cross
a cross analyzing the phenotypical results when two genes not on the same chromosome are observed
two genes are linked when
they are on the same chromosome and no recombination event is likely to happen during crossing over.
testcross
when an organism of dominant phenotype is crossed with an organism of homozygous recessive genotype.

if progeny= all Aa, then parental=AA
if progeny= 1/2 Aa and 1/2 aa, then parental= Aa
Mendel's Law of Independent Assortment
during anaphase I of meiosis there is a random assortment of maternal and paternal sister chromatids into each cell, thus contributing to genetic diversity
Dihybrid Cross Ratio
dominant dominant; dominant recessive; dominant recessive; recessive recessive. 9:3:3:1.
4 TtPp, 1 TTPP, 2 TtPP,2 TTPp
non-mendelian inheritance patterns
when clean concordance between genotype and phenotype is not exhibited in cases such as incomplete dominance or codominance.
incomplete dominance
an allele is incompletely dominant if the phenotype of the heterozygous genotype (Aa) is an intermediate between the two homozygous genotypes (aa and AA)
codominance
when there is more than one allele that is dominant when a population has more than two alleles for a gene. when both dominant alleles are in the genotype, characteristics from both are exhibited in the phenotype.
example of codominance
ABO blood groups;
homozygous recessive=Type O (ii)
homozygous dominant=AB,AA,BB
autosomes
non-sex chromosomes
sex chromosomes
chromosomes that determinen the organism's sex. XX=female
XY=male. Genes on these chromosomes are called sex-linked genes.
sex-linked traits
recessive X-chromosome traits that can be more easily seen in the male phenotype since males only have one X chromosome and therefore do not have another dominant allele to mask recessive traits passed on from the allele on the x-chromosome of his mother.
sex determination
x x

x xx xx

y xy xy

the chance of conceiving a male or female is fifty percent, no matter how many children the parents have already had.
examples of diseases that are x-linked
hemophilia, color-blindness
Traits that usually skip a generation are called...
sex-linked recessive traits (usually on the x chromosome but sometimes on the y). Female carriers (Aa) pass on the recessive trait to half their daughters and half her sons. Although her daughters will not be affected, the sons which receive the recessive allele will all be affected since this x-chromosome allele cannot be masked by another dominant allele from the father since the father only donates a heterologous y-chromosome. Afflicted males with the recessive trait thus can only pass on the trait through their daughters. All their daughters will be carriers, and half of the daughter's sons will be afflicted and half their daughters will be carriers. Fathers cannot pass on the recessive trait to their sons.
D. melanogaster is ideal for studying genetic traits because...
drosophila (fruit flies) are ideal because:
they have short life cycles, reproduce in large numbers, have relatively few chromosomes which are easily recognizable, and mutations occur relatively frequently in them.
environmental factors can affect the expression of a gene, such as..
The interaction between different environments and the same genotypes produces different phenotypes.
temperature; drosophila wing shapes are different in high and low temperatures; himalayan hares in low temperatures have black fur and in high temperatures have white.
Genetic problems can be caused by
mistakes during replication (cell division) such as nondisjunction or chromosome breakage which alters the number or structure of chromosomes. also, mutagens can cause mutations in somatic or sex cells (gametes). when mutations arise in gametes, there are hereditary consequences; somatic cell mutations do not have genetic implications--these result in tumors.
nondisjunction
occurs during meiosis I or meiosis II (during the production of the gametes). nondisjunction can result in trisomies or monosomies. most are lethal--cause spontaneous abortion of the embryo. trisomy 21 (Down syndrome) is not lethal.
number of chromosomes:

trisomy
monosomy
2N + 1

2N - 1
mutagenic agents
some are carcinogens. induce mutations. ex: cosmic rays, X-rays, UV rays, and chemical compounds such as mustard gas.
types of mutations
Single/multiple base pair:
substitution, addition, deletion (addition and deletions are frameshift mutations unless multiples of 3)
Silent mutations are substitution mutations which substitute for bases which do not affect the translation of the peptide and does not disrupt the structure and composition of the protein or enzyme.
examples of genetic disorders
phenylketonuria is a disease caused by the inability to metabolize phenylalanine due to the lack of functional enzyme.
sickle-cell anemia caused by the substitution of a single base pair...Val for Glu. This produces a defective hemoglobin which causes the red blood cell to sickle and cannot transport oxygen as well.
DNA
deoxyribonucleic acid; basic unit of heredity; self-replication ensures that its coded sequence will be passed on and changes made to the coded sequence when favorable, are maintained.
structure of DNA
basic unit of DNA is the nucleotide, made up of a deoxyribose (sugar), a phosphate group, and a nitrogenous base (purines and pyrimidines). has a sugar-phosphate backbone, complementary bases form the interior and bond to each other with double or triple hydrogen bonds to form the double helix. A always pairs with T and C always pairs with G. (Watson-Crick DNA model)
purines
Adenine and Guanine.
pyrimidines
Cytosine, Uracil and Thymine.
RNA
single stranded. has U instead of T. three types: mRNA, tRNA, rRNA.
mRNA
mRNA is messenger RNA, complement of DNA sequence assembled in the nucleus. monocistronic. transcription (synthesized) from 5' to 3'.
tRNA
small RNA found in the cytoplasm which aids in the translation of the mRNA to the polypeptide amino acid chain. tRNA has a three-dimensional clover-like structure including a site with the anticodon, onto which the mRNA is attached and a site for amino acid attachment.
aminoacyl-tRNA synthetase
the aminoacyl-tRNA synthetase attaches to the tRNA and to the amino acid. it catalyzes the attachment of the amino acid to its corresponding tRNA.
rRNA
ribosomal RNA are the structural components of ribosomes and are the most abundant of all RNA types. rRNA is synthesized in the nucleolus.
ribosomes
ribosomes are composed of a small and large subunit and rRNA. They have three binding sites:
the A site(aminoacyl-tRNA complex binding site)
the P site (peptidyl-tRNA binding site)
and a site for the mRNA.
The A site binds the incoming aminoacyl-tRNA complex, the P site binds to the tRNA attached to the growing polypeptide chain and catalyzes the formation of a peptide bond. The tRNA is expelled from the E site after translocation.
structure of DNA
basic unit of DNA is the nucleotide, made up of a deoxyribose (sugar), a phosphate group, and a nitrogenous base (purines and pyrimidines). has a sugar-phosphate backbone, complementary bases form the interior and bond to each other with double or triple hydrogen bonds to form the double helix. A always pairs with T and C always pairs with G. (Watson-Crick DNA model)
purines
Adenine and Guanine.
pyrimidines
Cytosine, Uracil and Thymine.
RNA
single stranded. has U instead of T and ribose instead of deoxyribose. three types: mRNA, tRNA, rRNA. can be found in both the nucleus and the cytoplasm.
mRNA
mRNA is messenger RNA, complement of DNA sequence assembled in the nucleus. monocistronic. transcription (synthesized) from 5' to 3'.
tRNA
small RNA found in the cytoplasm which aids in the translation of the mRNA to the polypeptide amino acid chain. tRNA has a three-dimensional clover-like structure including a site with the anticodon, onto which the mRNA is attached and a site for amino acid attachment.
aminoacyl-tRNA synthetase
the aminoacyl-tRNA synthetase attaches to the tRNA and to the amino acid. it catalyzes the attachment of the amino acid to its corresponding tRNA.
rRNA
ribosomal RNA are the structural components of ribosomes and are the most abundant of all RNA types. rRNA is synthesized in the nucleolus.
ribosomes
ribosomes are composed of a small and large subunit and rRNA. They have three binding sites:
the A site(aminoacyl-tRNA complex binding site)
the P site (peptidyl-tRNA binding site)
and a site for the mRNA.
The A site binds the incoming aminoacyl-tRNA complex, the P site binds to the tRNA attached to the growing polypeptide chain and catalyzes the formation of a peptide bond. The tRNA is expelled from the E site after translocation.
polypeptide synthesis
(translation: initiation, propagation, and termination)
1. small ribosome attaches to the mRNA.
2. large ribosome with sites A, P, and E attaches such that the P site lines up with the start codon (AUG).
3. aminoacyl-tRNA complex (trna + amino acid) for Methionine attaches at the P site (UAC)
5. next aminoacyl-trna complex corresponding to the next mRNA codon is attached to the A site.
6. peptidyl bond forms between the amino acid in the P site and the A site.
7. translocation occurs when the aminoacyl-trna complex from P shifts to E (and is thus released) and the aminoacyl-complex from A shifts to P.
8. stop codon on mRNA brings in the RF (release factor) to the A site causing the release of amino acid chain. Then, machinery separates.
each tRNA is charged with
a specific amino acid. charge=to aminoacylate
the anticodon for the start codon methionine is ___ from 5' to 3'
start codon is AUG (from 5 to 3)
anticodon is CAU.
translocation
ribosome advances 3 nucleotides along the mRNA sequence in the 5' to 3' direction.
in what direction is
...new DNA synthesized (replication)
...new RNA synthesized (transcription)
...mRNA read (translation)
5' to 3'
rRNA is synthesized in...
is found in...
nucleolus in nucleus.
cytoplasm
polypeptide synthesis terminates when one of these three codons are encountered
stop codons; UAA, UAG, UGA
this structure is formed when many ribosomes simultaneously translate a single mRNA molecule
polyribosome
polypeptides:
primary structure
secondary structure
tertiary structure
quaternary structure
amino acid sequence
intra/inter-molecular: disulfide bonds
alpha helices, beta sheets
supercoiling
cytoplasmic inheritance
systems of inheritance exist outside of the nucleus: genes from mitochondria, chloroplasts, and plasmids interact with nuclear genes to determine characteristics of organelles.