genetics intro

Question 1

genetic disease

Answer 1

caused by changes in genome

Question 2

hereditary disease

Answer 2

caused by genes inherited from the parents

Question 3

congenital disease

Answer 3

present from or before birth - due to genetic or environmental factors

Question 4

role of selective breeding

Answer 4

change appearance
reduce or eradicate hereditary diseases
improve productivity and fitness
improve resilience of populations to stresses/diseases
adapt animals to their current environment or function

Question 5

genes

Answer 5

a DNA segment at a specific position on genome that encodes a functional product

Question 6

allele

Answer 6

different forms of the same gene

Question 7

genotype

Answer 7

genetic makeup of an animal at one or more loci

Question 8

phenotype

Answer 8

end result - what we see/ measure

Question 9

examples of phenotype

Answer 9

coat colour
milk production
mastitis resistance

Question 10

qualitative traits

Answer 10

discrete
typically strong genetic component
controlled by a single gene
eg coat colour

Question 11

quantitative traits

Answer 11

counted or measured
influenced by non-genetic components
controlled by many genes
eg litter size, milk production, disease resistance

Question 12

homozygous v heterozygous

Answer 12

two copies of same allele v different alleles

Question 13

state Mendel’s 3 laws of inheritance

Answer 13

law of dominance
law of segregation
law of independent assortment

Question 14

what is the law of dominance?

Answer 14

some alleles are dominant and some are recessive

Question 15

what is non-additive gene action

Answer 15

alleles are considered either dominant or recessive

Question 16

what is complete dominance

Answer 16

homozygous dominant phenotype is the same as heterozygous phenotype

Question 17

what is incomplete (partial dominance)

Answer 17

heterozygous phenotype closer to homozygous dominant phenotype

Question 18

what is the law of segregation

Answer 18

parents pass on one allele to their offspring

Question 19

what is the law of independent assortment

Answer 19

genes of different traits are inherited independently of each other

Question 20

what is additive gene action

Answer 20

phenotype = genotype

Question 21

sex linked

Answer 21

genes on sex chromosome

Question 22

sex-limited

Answer 22

autosomal gene but phenotype only only present in one sex

Question 23

sex influenced

Answer 23

phenotype more common in one sex

Question 24

genomic imprinting

Answer 24

phenotype depends on the sex of the parent that contributes gene

Question 25

what is x - inactivation

Answer 25

one copy of the X chromosome becomes inactive in each cell early in embryo development

Question 26

what is epistasis

Answer 26

allele at one locus masks or enhances the effect of an allele at another locus = effect of one gene modified by another

Question 27

what is pleiotropy

Answer 27

allele at single locus affects multiple characteristics

Question 28

incomplete penetrance of phenotype variability

Answer 28

only a proportion of animals with genotype display phenotype

Question 29

variable expressivity of variability

Answer 29

different degrees of same phenotype eg polydactyl cats = all have extra digits but wide range of how many extra digits