Inheritance

Question 1

Define Epistasis

Answer 1

arises when the allele of 1 gene effects or masks the expression of another

Question 2

Define autosomal linkage

Answer 2

the inheritance of 2 or more genes carried on the same autosome

Question 3

Define sex linkage

Answer 3

inheritance of a gene found on the x or y chromosome

Question 4

Define multiple alleles

Answer 4

when a gene has more than 2 alleles

Question 5

Define co-dominant alleles

Answer 5

alleles that are both expressed in the phenotype when they occur in a heterozygous individual

Question 6

Define di-hybrid inheritance

Answer 6

the inheritance of 2 different genes on different chromosomes at the same time

Question 7

Define monohybrid inheritance

Answer 7

the inheritance of a single gene on an autosome

Question 8

Define heterozygous

Answer 8

an organism with 2 different alleles on each chromosome- one will be dominant and one recessive

Question 9

Define homozygous recessive

Answer 9

an organism with 2 of the same alleles on each chromosome where both are recessive

Question 10

Define homozygous dominant

Answer 10

an organism with 2 of the same alleles on each chromosome where both are dominant

Question 11

Define allele

Answer 11

a different version of a gene

Question 12

Define genotype

Answer 12

the genetic constitution of an organism, describing all the alleles that the organism contains

Question 13

Define phenotype

Answer 13

the expression of the genetic constitution and its interaction with the environment

Question 14

Define gene

Answer 14

a base sequence of DNA on a chromosome which codes for the amino acid sequence of a polypeptide or a function RNA

Question 15

State reasons why the observed phenotypic ratios may be different from the expected ratios

Answer 15

Random fertilisation of gametes
Maybe a small sample size
Maybe a lethal genotype
Maybe be linked genes
Maybe epistasis

Question 16

How do multiple alleles of a gene arise?

Answer 16

Random mutation

Question 17

Which sex is more likely to express the recessive alleles found on their sex chromosomes in their phenotype?

Answer 17

Males
they only have 1 copy of the x chromosome so only need one copy of the recessive allele in their genotype to express the recessive phenotype, whereas females have 2 x chromosomes so need 2 copies of the recessive allele in their genotype to express the recessive phenotype.

Question 18

What is phenotype frequency?

Answer 18

how often a phenotype appears in a population. This is easy to measure as we can see the phenotype.
Frequencies are always given as a number between 0-1

Question 19

What is genotype frequency?

Answer 19

how often a genotype appears in a population

Question 20

Why is genotype frequency hard to measure?

Answer 20

An organism with a dominant phenotype might be homozygous dominant or heterozygous, you can’t tell.

Question 21

What is allele frequency?

Answer 21

how often a particular allele appears in a population

Question 22

Give the Hardy- Weinburg equations

Answer 22

p + q = 1
p2 + 2pq + q2 = 1

Question 23

State the assumptions made by the Hardy- Weinburg equations

Answer 23

1. Mating is random
2. There is no immigration so new alleles introduced
3. There are no mutations so no new alleles created
4. There is no selection so no alleles favoured or eliminated
5. The population is large

Question 24

Whats the equation for degrees of freedom?

Answer 24

n-1