Genetics, population, evolution and ecosytems Ch. 17, 18, 19 Flashcards
Gene
A section of DNA, (a sequence of nucleotide bases) that codes for a polypeptide chain
Universal
Same DNA in a range of organism
Diploid
A cell containing two complete sets of chromosomes, one from each parent
Genome
All the genes contained within one cell including the mitochondria and chloroplast
Locus
The position/location of a gene on a chromosome
Degenerate
More than one triplet code codes for the same amino acid
Allele
An alternate form of a gene/ One of the different forms of the gene
Histone
The protein around which DNA is folded around the nucleus
Homologous chromosomes
A pair of chromosomes where one is provided by the mother and one by the father
Proteome
The full range of proteins coded for by a genome
Intron
Sequences of non-coding DNA
Exon
Sequences of coding DNA
Chromosome
One of the two thread-like strands from when a chromosome divides
Non-overlapping
Each base does not code for more than one amino acid. Each base is only read once.
Genotype
The genetic make up of an organism.
Phenotype
the characteristic of an organism , often visible, as a result of both phenotype and the environment
How many alleles of a gene can there be on one chromosome?
One
Homozygous
When the alleles of a gene are the same on both chromosomes.
Heterozygous
When the alleles of a gene are different.
Dominant allele
An allele that is always expressed in the phenotype of an organism
Recessive allele
The effect of the allele is shown as the phenotype in a diploid organism when there is two of the recessive allele
Homozygous Dominant
When both alleles are dominant
Heterozygous Recessive
When both alleles are recessive
Codominant
When the two alleles contribute to the phenotype. It results in either a blend of both or both being shown.
Multiple alleles
When a gene has more than two allele forms. (still only two of the forms can ever be present).
Mutation
Any change to the genotype due to change in DNA, which can then be inherited.
Modification
Change in phenotype, which is not inherited (e.g piercing)
Monohybrid inheritance
The inheritance of a single gene
Pure-breeding
When the alleles are homozygous
First Filial generation
The offspring of the parents (F1)
Second Filial generation
The offspring of two F1s
How many alleles of a gene can there be in a gamete?
One
How many alleles of a gene can there be in a cell
Two
How do you calculate ratios?
Divide the numbers by the smallest number. That way you will always get 1:
When is it most likely that actual results will be close to theoretical results?
When there is a large sample size.
Dihybrid inheritance
Two different genes and characteristics are inherited.
How would you get the genotypes from RrGg?
Think expand the brackets (Rr)(Gg). RG Rg rG rg
What’s the rato for RrGg and RrGg?
9: 3: 3: 1
What’s the Law of Independent assortment?
Each allele may combine randomly with another.
IA IB IO, which are codominant and recessive?
IA and IB are codominant, IO is recessive.
How many chromosomes does a human cell have?
46, 23 pairs
What are the female and male sex chromosomes?
XX Girls, XY Boys
Why is it said that males determine the sex of the offspring?
As all female gametes will have an X, whereas the male gametes will have either X or Y. Therefore, if the male gamete is the X the offspring will be a girl, but if its a Y is will be a male.
What is a sex-linkage?
A gene that is on the X or Y chromosome.
Why is there generally no homologous genes on both X and Y?
Because the X chromosome is longer than the Y .
Why is it more likely for males to get diseases that are X recessive?
As males only have one X chromosome and therefore only one allele and no dominant, therefore the recessive allele is presented.
Give an example of sex-linked disease
Haemophilia, which slows down clotting. Confined mainly to males because females die with it and males only have one X chromosome.
Why is it said that in a male haemophilia is inherited from his mother?
Its a allele carried on the X chromosome which can only come from the mother.
What is an Autosome?
Any chromosome that is not the sex chromosomes
What is Autosomal linkage?
Any two or more genes that are on the same chromosome
Assuming there is no cross-over what happens to linked genes in meiosis?
Linked genes will be in the same gamete because they are transferred together.
What determines blood type?
The antigens on the cell-surface membrane of red blood cells.
What blood type do you have if you have IA IO?
A
What blood type do you have if you have IA IA?
A
What blood type do you have if you have IA IB?
AB
What’s epistasis?
When the allele of one gene affects or masks the expression of another in the phenotype.
What is wild type?
A gene or characteristic of a species that occurs in nature, so not a mutant allele.
What is back crossing?
When an offspring is breed with its parent.
How many type of gametes can be produces in an autosomal linkage?
Only ever two.
What is dominant epistasis?
When it’s the dominant allele in the epistatic allele that masks/ affects the other gene.
What is recessive epistasis?
When it is a recessive allele in the epistatic allele that masks/affects the other gene.
When is the chi squared test used?
To test the null hypothesis. If there is a statistically difference between the sets and if it is due to chance
What is a null hypothesis?
There is no statistically significant difference between x and y and and difference is due to chance
What is the formula for chi squared?
Sum of [ observed number - expected number)^2 / expected number ]
How do you calculate the degrees of freedom?
Number of categories - 1
What is the percentage to look at for the critical value
0.05 / 5%
When do you accept or reject the null hypothesis?
Reject if the number is bigger than the critical value, accept if smaller.
If the x^2 at 0.99 for 3 degrees of freedom is 1.2. And your x^2 gave you 1. What would you conclude?
You can accept the null hypothesis with 99% confidence so there is no statistically significant difference and any difference is due to chance.
If the x^2 at 0.99 for 3 degrees of freedom is 1.2. And your x^2 gave you 1.5, what would you conclude?
You cannot accept the null hypothesis with 99% confidence.
If the x^2 at 0.01 for 3 degrees of freedom is 6.4 . And your x^2 gave you 5, what would you conclude?
You cannot reject the null hypothesis with 99% certainty but can accept the null hypothesis with 1% certainty.
If the x^2 at 0.01 for 3 degrees of freedom is 6.4 . And your x^2 gave you 6.6, what would you conclude?
You can reject the null hypothesis with 99% certainty therefore the is a statistically significant difference and any difference is not due to chance.
Suggest reasons for why observed ratios are not often the same as expected?
- Fertilisation is random
- not large enough sample size
- There may be a more advantageous or disadvantageous allele ;
Population
A group of organisms of the same species occupying a particular space that can potentially interbreed.
Gene pool
All the alleles of all the genes of all individuals in a populations at any given time
Allele frequency
The number of times an allele occurs within the gene pol.
What is the Hardy-Weinberg principle?
A mathematical model which predicts that allele frequency will not change from generation to generation.
When does the Hardy-Weinberg principle work?
When there is : No mutations, no migration, no selection, large population and mating is random.
Give the two equations for the Hardy-Weinberg principle
p + q = 1
p^2 + 2pq + q^2 = 1
What is the genetic factors for variation within a population?
Mutation, meiosis and recombination and random fertilisation of gametes.
What is the environmental factors for variation within a population?
Competition for resources, disease and predation
Intra-specific competition
Within a species
Inter-specific competition
Between a species
What is a selection factor?
The environmental factor limiting the population of a species.
Disruptive selection
Favours both extremes and the mean is selected against
Directional selection
Favours one extreme from the mean
Stabilising Selection
Favours the mean and goes against the extreme ends.
Continuous Variation
a continuous range of values
Discontinuous Variation
Values are in categories
What does evolution do to the allele frequency
Changes the allele frequency
Speciation
The evolution of a new species from existing ones.
