Inheritance

Question 1

Locus

Answer 1

Position of a gene on a particular DNA molecule

Question 2

Co dominant

Answer 2

Both alleles are expressed

Question 3

Polygenic inheritance

Answer 3

Many genes that control one characteristic

Question 4

Recessive allele

Answer 4

Only expressed if both the organisms alleles are recessive

Question 5

Dominant allele

Answer 5

The allele is always expressed

Question 6

Allele

Answer 6

Different form of the same gene

Question 7

Gene

Answer 7

Small section of DNA that coded for a specific protein

Question 8

Homozygous

Answer 8

2 of the same alleles

Question 9

Heterozygous

Answer 9

2 different alleles

Question 10

Phenotype

Answer 10

How the gene is expressed and its interaction with the environment

Question 11

Genotype

Answer 11

Genetic constitution of an organism (all the alleles an organism has)

Question 12

What is the name for any change to a genotype

Answer 12

Mutation

Question 13

Law of segregation (for monohybrid)

Answer 13

In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete.

Question 14

Monohybrid inheritance

Answer 14

• Is a mating between two individuals in which the phenotype (character) is controlled by a single gene (one genetic locus) which has two or multiple alleles.
• test/cross to investigate he genotype of an unknown organism

Question 15

Why are actual results of a genetic cross rarely the same as predicted?

Answer 15

• discrepancies are due to statistical errors

- the larger the sample the more likely the actual results come near to matching the theoretical ones

Question 16

Dihybrid inheritance

Answer 16

A mating experiment between 2 organisms showing the results of 2 traits/genes
A hybrid organism is one that is heterozygous, meaning it carries 2 different alleles at a particular genetic position or locus
Get a 9:3:3:1 ratio

Question 17

Law of independent assortment (for dihybrid)

Answer 17

Each pair of alleles for a particular gene can combine randomly with either of another pair of alleles from another, different gene

Question 18

Co dominance explained

Answer 18

• both alleles expressed in the phenotype
• both equally dominant therefore both expressed
• when representing the alleles, they have a different capital letter which is written as a superscript on a letter that represents he gene
• F2 ratio is 1:2:1

Question 19

Multiple alleles

Answer 19

Where there are more than two alleles of which only two may be present at the loci of an individuals homologous chromosomes

Question 20

Sex linkage

Answer 20

Y chromosomes are shorter and so miss the sex linked allele that are on the long arm
Represent the crosses using the chromosomes letter and a superscript for alleles

Question 21

Autosomal linkage

Answer 21

• the loci of 2 or more different genes are on the same chromosome
• the results DO NOT obey the law of segregation as they don’t segregate
• any two genes on the same chromosome are linked
• all genes on a single chromosome form a linkage group
• assuming no crossing over, all the linked genes remain together during meiosis and so pass into the gametes and offspring
• get a 3:1 ratio
• excluding the sex chromosome all the other 22 are called autosomes

Question 22

Epistasis

Answer 22

When the allele of one gene affects or masks the expression of another in the phenotype
You get a 9:4:3 ratio not 9:3:3:1

Question 23

What is the hardy Weinberg principle?

Answer 23

The proportion of dominant and recessive alleles in a population remains constant from one generation to the next.

Question 24

What are the 5 conditions for the hardy Weinberg principle to be met?

Answer 24

• no mutations
• population isolated
• no selection
• large population
• mating within the population is random

Question 25

What is the hardy Weinberg formula?

Answer 25

p2 + 2pq + q2