Gene Interaction, genetic code and gen

Question 1

Incomplete dominance

Answer 1

blending the parental traits (making third phenotype)

polygenic type of inheritance - ex coat and eye colour

Question 2

co dominance

Answer 2

both parental traits occur together

both alleles completely expressed

Question 3

Epistasis

Answer 3

Multiple loci affecting two different loci

-their effects are NOT additive

Question 4

Epistasis occurs:

Answer 4

• whenever two or more loci interact to create new phenotypes
• whenever an allele at one locus masks the effects of alleles at one or more other loci
• whenever an allele at one locus modifies the effects of alleles at one or more other loci

Question 5

Epistasis is an interaction at the _____ level of organization

Answer 5

phenotypic

Question 6

Cream dilution gene in horses

Answer 6

creates palomino and cremello from chestnut base colour

• cream dilution gene has two alleles Car and C
• Ccr allele is semidominant; it dilutes red to yellow in heterozygous state and red to pale cream in homozygous state
• C allele has no diluting effect on coat colour

Question 7

eeCC

Answer 7

red coat colour

Question 8

eeCCcr

Answer 8

palomino (gold coat with a white mane and tail)

Question 9

eeCcrCcr

Answer 9

cremello

Question 10

Mimic genes

Answer 10

mutations in different genes (different loci) with same phenotype
-wiry hair coat in cats (rex cats, La perm, American wirehair)

Question 11

Pleiotropy

Answer 11

Multiple and varied effects of a single gene

-one gene affecting multiple tissues (stem cell migration)

Question 12

Examples of Plieotrophy

Answer 12

white cats often, but not always
merle color and deafness
Lavender foal syndrome

Question 13

Mutlifactorial traits

Answer 13

continuous scale- not categorical as mendelian traits

• independent genes at different loci
• strong environmental influence
• measured using a scale

Question 14

performance trait

Answer 14

size (weight and height), milk yield, speed,

Question 15

Diseases

Answer 15

OA
HD
Disc prolapse
OC
Wobbler

Question 16

Polygenic traits

Answer 16

familial
severity scale
increased incidence with inbreeding
environmental influence

Question 17

2 types of polygenic traits

Answer 17

threshold trait
dominant gene(s) + modifying genes

Question 18

Liability

Answer 18

probability of being affected (genotype and environment)

individual parameter

Question 19

Threshold

Answer 19

level of liability above which all animals show the trait

population parameter

Question 20

Expressivity

Answer 20

• all animals with the genotype show the phenotype, but to varying degrees
• refers to individual variability
• degree of variation in the severity of the defect
• variable expressivity - signs are always present

Question 21

Penetrance

Answer 21

• polygenic trains mainly controlled by one gene
• either express the phenotype or not
• incomplete penetrance
• POPULATION VARIABILITY
• can be quantified

Question 22

Phenocopies

Answer 22

-environment mimics the effect of a genotype

Question 23

Heritability=

Answer 23

Vg/ (Vg+Ve)

-variance of genotype/ variance of phenotype

Question 24

5 levels of genetic control

Answer 24

1. transcription control- gene on DNA
2. RNA processing control- primary transcript
3. RNA transport control- mRNA
4. Translation control- protein
5. Post translation control - modified protein

Question 25

RNA splicing occurs?

Answer 25

in the nucleus

Question 26

Codons vs anti-codons

Answer 26

condons are the code on the mRNA

anti-codons are the code on the tRNA

Question 27

Reading frame reads until

Answer 27

TAA
TAG
TGA

Question 28

Mutations

Answer 28

=uncorrected mistakes in DNA replication which alter the DNA sequence

• somatic mutations - individual
• germ-line mutations - familiar

Question 29

Types of mutations

Answer 29

point mutations
-substitutions- transition and transversion
-insertions
-deletions
Larger insertions and deletions
Splice mutations - mutations at the interface of axons and introns -introns remain in mRNA

Question 30

Consequences of mutations

Answer 30

mis-sense
-altered AA sequence
Nonsense
-preamture stop codon
Silent
-condon redundancy so new codon, but same AA

Question 31

SNP

Answer 31

variation at a single position in a DNA sequence among individuals

• if more than 1% of a population does NOT carry the same nucleotide at a specific position this variation can be classified as a SNP
• if a SNP occurs within a gene, then the gene is described as having more than one allele
• SNPs can lead to variations in AA sequence

Question 32

Epigenetic control

Answer 32

=how access to genes are regulated within the chromosome

• access to genes= acetylation of histone tails and DNA dementhylation
• murder of gene expression= methylation of DNA

Question 33

X inactivation

Answer 33

females or individuals with two X chromosomes

• alleles on one X chromosome inactivated during embryogenesis
• each cell have different active allele
• x inactivation is random among alleles and not specific in time during embryogenesis

Question 34

Imprinting

Answer 34

Monoallelic expression
-X inactivation in BOTH sexes
Origin of gene important - expression is parent of origin specific
Does NOT follow mender’s law of monogenic inheritance
Gene from father acts differently than gene from mother

Question 35

Noncoding RNA and post-transcriptional regulation

Answer 35

• epigenetics and silencing of genes affects what sections of DNA are being transcribed
• area of small RNA guided gene silencing
• mRNA is for example often degraded or prevented from being translated by microRNAs
• microRNAs more stable than mRNA and sometimes cell and tissue specific

Question 36

Mitochondrial inheritance

Answer 36

• maternal inheritance
• imparied energy production
• threshold effect- random allocation in number of mitochondria into oocytes during oogenesis
• affected males do not pass on disease
• affected or carrier females may or may not pass on defect