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39 Cards in this Set
- Front
- Back
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Gene |
A specific section of DNA/Chromosome that codes for a particular protein/feature/characteristic/trait. The sequence of ATGC bases at that section codes for the particular protein/trait. |
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Chromosome |
A long length of DNA organised into threadlike structures of DNA and protein. Found in the nucleus of cells - carries the genetic information in the form of genes. |
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Alleles |
Different forms of the same gene they can be dominant or recessive. Made of DNA. These code for the same kind of trait but may result in slightly different proteins/traits due to the different sequence of ATGC’s found at that gene. |
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Dominant |
The allele which is always expressed (seen in the phenotype) even if only one is present. Written with a capital letter eg. R. It will mask or hide the effect of the recessive allele. |
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Recessive |
The allele that will only be expressed/ show in the individual if the dominant allele is not present. Written with a lowercase letter e.g “r” |
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DNA |
What chromosomes are made of, made up of linked nucleotides (a phosphate, a sugar and a base ( of either ATCG) 2 strands in a double helix formation. Carries the organism’s genetic information and determines phenotype. |
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Nucleus |
The cell part that contains the chromosomes |
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Base |
The part of the DNA that makes up its structure and involved in base pairing: A (Adenine) with T (thymine) and C (cytosine) with G (guanine). Base pairing is very important for ensuring accurate DNA replication. |
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Homologous chromosomes |
Chromosomes that have the same structural features (length) and pattern of where specific genes are found .You inherit one from your mother and one from your father. They pair up and line up during meiosis to form gametes/sex cells. |
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Nucleotide |
forms the basic structural unit of DNA, composed of a sugar molecule, a phosphate group and a base. |
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Trait |
Genetically determined characteristic |
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Variation |
Phenotypic differences between organisms within a population - can be discontinuous or continuous.Very important for a population and species survival when faced with environmental change. |
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Phenotype |
The organism’s observable characteristics or traits based on the genotype. (Genotype is the specific combinations of alleles the individual has). |
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Genotype |
The particular alleles of an organism.Written as a combination of 2 letters eg. RR, Rr or rr. |
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Mitosis |
The cell division body cells use for growth and repair.Produces 2 new daughter cells genetically identical to each other and to the parent cell. |
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Meiosis |
The cell division that occurs in testes/ovaries to produce 4 new gametes/sex cells.These sex cells are genetically unique to each other & the parent cell and have half the normal number of chromosomes as body cells. |
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Fertilisation |
Random male and female gametes/sex cells join, producing a genetically unique zygote.It is random which alleles are passed on when creating gametes in meiosis and which eggs/sperm/pollen gets fertilized thus creating unique zygotes and individuals. |
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Gamete |
Sex cells or eggs/sperm/pollen.Genetically unique to create genetic variation in the population and with half the number of chromosomes compared to the parent cell from the testes or ovaries. |
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Zygote |
A fertilized ovum/egg that contains the full set of chromosomes and is a genetically unique individual. |
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Asexual Reproduction |
Reproduction involving only 1 parent (usually female) the offspring contain the genetic material/DNA of the parent and are genetically identical to the parent and to each other. |
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Sexual Reproduction |
reproduction involving two parents - the offspring contain a unique mix of genetic material/DNA from each parent. The offspring are genetically different to the parent and to each other. |
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Pure breeding |
Individuals that are homozygous - will always produce the same offspring when crossed together. |
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Homozygous |
An individual/Genotype with two alleles that are the same for a particular trait.Can be homozygous dominant eg RR (two dominant alleles)or Homozygous recessive eg rr (two recessive alleles) |
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Mutation |
a permanent change in the base sequence of DNA.If the mutation occurs in a body cell eg skin cell it cannot be inherited by offspring. If it occurs in a gamete/sex cell it can be inherited and passed onto offspring.Mutations create new alleles and can change the traits and proteins an organism has and these can be helpful or harmful to the organism . They contribute to genetic variation if not so harmful that they kill the organism. |
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Heterozygous |
An individual/genotype with two alleles that are different for a particular trait. Eg Rr one dominant and one recessive. |
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Test cross |
cross between an unknown genotype organism and a homozygous recessive to work out the genotype from the resultant offspring. |
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pedigree chart |
diagram/family tree that shows the phenotypes of related individuals.When explaining why a particular individual has a particular genotype/phenotype on a chart you must explain how the individual must have received one allele from each parent (be that dominant or recessive) and then use the pedigree chart and the individual numbers as examples. |
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Haploid |
Having a single set of chromosomes (n). Often seen in sex cells/ gametes with half the normal chromosome numbe |
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Diploid |
Having a full set of chromosomes (2n) having a pair of each type of chromosome.Mostly seen in body cells and zygotes. |
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Carrier |
a heterozygous individual Eg Rr that carries an allele for a particular recessive trait, doesn’t express the trait but can pass that trait on to their offspring. |
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Double helix |
the structure of DNA - two strands of nucleotides wound around each other. |
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DNA replication |
When DNA replicates itself entirely to make 2 identical DNA molecules in a cell.Happens before the mitosis and meiosis cell divisions. |
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Semi-conservative replication |
In each new DNA double helix, one strand is from the original molecule and one strand is new from new nucleotides. |
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sex chromosomes |
Chromosomes X and Y that determine the sex of an individual. XX is female and XY is male |
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Crossing over |
Exchange of pieces of genetic material from two homologous chromosomes.Occurs when homologous chromosomes pair up during meiosis - contributes to the genetic variation possible in the gametes by reshuffling the possible alleles from their parents. |
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Independent assortment |
Each homologous chromosome pair (paternal or maternal) lines up at the equator in a random assortment, independently of other homologous pairs; before being separated into new gamete cells. By the time the process of meiosis is finished the homologous pairs are divided in two and the gamete will inherit one of each pair of chromosomes. which of the pair (paternal or maternal) is passed on is random due to this process of independent assortment. This contributes to genetic variation |
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Changing environment |
Examples of environmental change that could affect the survival or reproductive success of an individual. Eg. pest infestation, disease drought, flood, food change, new predator etc.Genetic variation is important for the species to survive in such an environment as some individuals may survive because of their particular traits. These will then go on to breed and pass on their alleles and their characteristics to their offspring thus changing the phenotypic ratios of future generations |
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F1 generation and F2 generation |
Name for the offspring of the first cross eg. BB x bb and their offspring = F1 and their offspring is F2 |
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Proteins |
Made up of amino acids. These are what most of your body is composed of. There are many types and all have important roles in living systems and cells.A lot of genes are codes for making proteins in cells. |
