Unit 3: Introduction to animal genetics (Lecture 1-2)

Question 1

What is a gene ?

Answer 1

Part of the DNA sequencing that encodes a protein

Question 2

What is an allele ?

Answer 2

Different forms of the same gene

Question 3

What is the genotype ?

Answer 3

The combination of alleles for a gene locus

Question 4

What is Mendel’s first principle ?

Answer 4

The principle of segregation

Question 5

What is the principle of segregation ?

Answer 5

That for any particular trait during gamete formation the two alleles in each parent separate and only one allele is passed to the offspring

Question 6

What is a monohybrid cross ?

Answer 6

A genetic cross that examines the inheritance of a single trait

Question 7

What statistical test can be used to confirm the principle of segregation ?

Answer 7

Chi squared

Question 8

What is Mendels second principle ?

Answer 8

The principle of independent assortment

Question 9

What is the principle of independent assortment ?

Answer 9

• That when a parent is segregating two or more gene loci, alleles for each gene are passed to the offspring independently of each other
• Combinations of phenotypes present in neither parent will be produced

Question 10

What is a dihybrid cross ?

Answer 10

A cross that examines the inheritance of 2 genes simultaneously

Question 11

What is the F2 ratio for a dihybrid cross ?

Answer 11

9:3:3:1

Question 12

What is a wild type allele ?

Answer 12

A normal, unaltered allele

Question 13

What is the predominant allele at the gene locus in the population ?

Answer 13

The wild type allele

Question 14

What are the 3 types of alleles ?

Answer 14

1) Loss of function alleles
2) Gain of function alleles
3) Isoalleles

Question 15

What is a loss of function allele ?

Answer 15

• Where the gene product has reduced activity compared to the wild type
• Tend to be recessive to wild type
• Has no overall effect on the phenotype
• Seen in lactose intolerance

Question 16

What is a gain of function allele ?

Answer 16

• Where the gene product has increased activity with respect to wild type
• Generally dominant to wild type
• Involved in cancer

Question 17

What is a isoallele ?

Answer 17

• Neutral allele
• Mutant allele has same action as wild type allele

Question 18

What are the 5 modes of inheritance leading to genetic disease in domestic animals ?

Answer 18

1) Autosomal dominant
2) Autosomal recessive
3) X linked recessive
4) Sex limited inheritance
5) Polygenic or complex

Question 19

What is an autosome ?

Answer 19

Anything that is not a sex chromosome

Question 20

What is autosomal dominance ?

Answer 20

• Gene on autosome
• Only one copy of mutated allele needed for phenotype
• Passes from one generation to the next without skipping a generation

Question 21

Give an example of autosomal dominance in cats

Answer 21

Lack of tail in Manx cats

Question 22

What is autosomal recessive ?

Answer 22

• Gene on autosome
• Two copies of mutated allele required for phenotype
• Commonest mode of inheritance of single gene disorders in domestic animals
• Can skip many generations
• Frequency increases with inbreeding

Question 23

Give an example of autosomal recessive in bulls

Answer 23

Double muscling, extreme muscularity in proximal fore and hindquarters

Question 24

What is incomplete penetrance ?

Answer 24

When offspring has the genotype but does not express the phenotype

Question 25

What is X-linked recessive ?

Answer 25

- Where the gene is on the X chromosome - Usually males are affected and females are the carriers

Question 26

Give 2 examples of X-linked recessive in dogs

Answer 26

- Haemophilia A in dogs- Failure of blood clotting - Von Hillebrands disease- blood clotting disorder

Question 27

What is sex linked inheritance ?

Answer 27

When the gene is on an autosome but the condition is only expressed in one sex

Question 28

What is polygenic inheritance ?

Answer 28

Genotype and environment interaction

Question 29

What does it mean when a trait is said to be multifactorial ?

Answer 29

When a large number of factors, both genetic and environmental are involved

Question 30

What are the 2 Hardy Weinberg equations ?

Answer 30

p^2 + 2pq + q^2 = 1 p + Q = 1

Question 31

What letter can be used to represent affected individuals ?

Answer 31

q^2

Question 32

What letter can be used to represent the frequency of carriers ?

Answer 32

2pq

Question 33

If allele frequencies deviate from hardy Weinberg equilibrium than what 4 things need to be considered ?

Answer 33

1) If one allele is advantageous 2) Genetic drift 3) Denovo mutations 4) Non random mating

Question 34

What is a mutation ?

Answer 34

An error in the replication of DNA or in the separation of chromosomes during cell division

Question 35

What are the two categories of mutation ?

Answer 35

1) Point mutations 2) Chromosome mutations

Question 36

What is a point mutation ?

Answer 36

Altered nucleotide sequence of a gene such as substitutions, insertions or deletions. Uncorrected mistakes during DNA replication

Question 37

What is a chromosome mutation ?

Answer 37

Errors during cell division such as translocations, deletions and alterations in chromosome number

Question 38

What are the 5 types of chromosome mutation ?

Answer 38

1) Translocation 2) Inversion 3) Deletion 4) Duplication 5) Chromsome disjunction

Question 39

What is translocation ?

Answer 39

Where one piece of chromosome is moved to another, often reciprocal with swapping of material

Question 40

What is an inversion ?

Answer 40

Where segments of the chromosome flips its orientation with respect to the rest of the chromosome

Question 41

What is a deletion ?

Answer 41

Where a large segment of chromosome is deleted resulting in the loss of a number of genes

Question 42

What is a duplication ?

Answer 42

Where some genes are duplicated on the same chromosome

Question 43

What is chromosome non-disjunction ?

Answer 43

Where chromosomes fail to separate during cell division resulting in one daughter cell having an extra chromosome and the other daughter cell lacking one

Question 44

What are the 6 types of single base mutations ?

Answer 44

1) Silent mutation 2) Nonsense mutation 3) Missense mutation 4) Splice site mutation 5) Insertion 6) Deletion

Question 45

What is a single nucleotide polymorphism ?

Answer 45

- A point mutation - Represents the rare allele (frequency of at least 1%)