Genetics, populations, evolution and ecosystems Flashcards
definition of phenotype
visible characteristics in an organism, determined by the genotype and its environment
definition of genotype
the genetic makeup of an organisms, by the combination of alleles found
definition of codominance
both alleles contribute to and are expressed in the phenotype
definition of multiple alleles
when a gene has more than two alleles
definition of a dominant allele
an allele that is always expressed in the phenotype of an organism
definition of recessive allele
an allele that is only visible in the phenotype in the presence of another identical allele
definition of homozygous
the alleles for a particular gene are identical
definition of heterozygous
the alleles for a particular gene are different
definition of diploid
nucleus contains two sets of chromosomes (homologous pairs)
definition of haploid
the nucleus contains only one copy of each chromosome
what is dihybrid inheritance
inheritance of two characteristics, determined by two different genes on different chromosomes at the same time
how do we work out gamete combinations in dihybrid inheritance
FOIL
F - first
O - outside
I - inside
L - last
what are the gamete genotypes of Round (R) Yellow (Y) seeds if the alleles for both yellow and round are dominant, as opposed to green (y) and shrivled (r). The gametes are heterozygous
Genotype: RrYy
gamete genotypes: RY, ry, Ry, rY
what are the chromosome representations for a boy
XY
what are the chromosome representations for a girl
XX
any gene that is on the X or Y chromosome is said to be ….
sex linked
if the parents phenotype is XX for female and XY for male, what are the gametes?
And what is the ratio of which offspring they will have
X or X and X or Y
1:1 ratio
what is a gene
a length of DNA that codes for a specific polypeptide
what is an allele
a part of the DNA base sequence that codes for the alternative form of a gene at a specific loci
A gene controlling coat colour in cats is sex linked. The two alleles of this gene are black and orange. When both are present the coat colour is called tortoise shell. Explain why there are no male tortoise cats
the gene is only on the X chromosome, and males cats only have one X
So male cats can only have one coat colour as only one out of the homologous pairs can code for a coat colour
and two coat colour alleles are needed for a tortoiseshell coat
what is meant by the term sex linked
traits or disorders that are influenced by the genes on a sex chromosomes
definition of population
a group of organisms of the same species in a particular place at a particular time and have the potential to interbreed
what is a gene pool
all the alleles of all the genes of all the individuals in a population at a given time
what is allelic frequency
the number of times an allele occurs within a gene pool
What is the Hardy-Weinberg equations we need to remember
p² + 2pq + q² = 1.0
p + q = 1.0
what are some assumptions we make when using the hardy-weinberg equation
- no mutations arise
- the population is isolated, so no immigration or emigration
- no allelic selection occurs, so both alleles are equally as likely to be passed onto the next generation
- large population is being sampled
- mating within the population is random and NOT controlled, so no interbreeding
what does p² stand for in the Hardy Weinberg equation
the percentage/proportion of homozygous dominant individuals
what does q² stand for in the Hardy Weinberg equation
the percentage/proportion of homozygous recessive individuals
what does 2pq stand for in the Hardy Weinberg equation
the percentage/proportion of heterozygous individuals
what does p stand for in the Hardy Weinberg equation
the frequency of dominant alleles in a population
what does q stand for in the Hardy Weinberg equation
the frequency of recessive alleles in a population
Cystic fibrosis is an autosomal recessive genetic disorder.
4 in 10,000 newborn babies in the United Kingdom have the disease.
Use the Hardy-Weinberg principle to estimate the percentage of UK newborns that are carriers for cystic fibrosis.
Give your answer to one decimal place.
In a population of 10,000 UK newborn babies, the expected proportion of babies having the disease is 4/10,000 = 0.0004 = q2.
The frequency of the allele that causes the disease (q) if the square root of this number, 0.0004 = 0.02.
You know that p + q = 1, therefore p = 1 – 0.02 = 0.98. Now, you can calculate the expected frequency of the three genotypes:
p2 (homozygous dominant; normal) = 0.9604
2pq (heterozygous; normal but carrier) = 0.0392
q2 (homozygous recessive; cystic fibrosis) = 0.0004
Therefore 3.9% of UK newborns are carriers of cystic fibrosis.
what do we use chi squared to find
whether there’s a difference between expected and observed result
if i have a null hypothesis for a t test, what do we say
that theres no statistically significant difference between results and that they are due to chance
if i have a alternative hypothesis for a t test, what do we say
that there is a significantly significant difference between results and that they are not due to chance
What is epistasis
when two genes (usually on different chromosomes) interact together to affect the phenotype. An allele of one gene may affect or mask the expression on another gene.
