Mendelien genetics - week 14

Question 1

What is a gene

Answer 1

Unit of heridetitary info consisting of a specific nucleotide sequence in DNA (ran in viruses)

Question 2

Model organism (non-human studied species)

Answer 2

Short gen time
many offspring
easy/ cheap to grow
easy to cross/ fertilize

Question 3

Homozygous

Answer 3

Both alleles at locus are the same

Question 4

Heterozygous

Answer 4

Both alleles at locus are different

Question 5

The standard 3;1 ratio produced by Rr x Rr shows what

Answer 5

Alleles involved show complete dominance or recessiveness

Question 6

Mandels 1st law

Answer 6

The two alleles for a heritable characterist segregate during gamete formation and end up in different gametes

Question 7

Mandels 2nd law

Answer 7

Each character is independantly inherited during gamete formation
Law of independent assiotment

Question 8

Exceptions to mandels law

Answer 8

Incomplete dominace and co-dominance - interactions at same loci

Epistasis - interactions at different loci

Question 9

What is incomplete dominance

Answer 9

Both alleles are domiant so there’s a blending of the two traits

Question 10

What is co-domiance

Answer 10

both alleles contribute to the phenotype of the organism by showing up simaltaniously

Question 11

What is epistasis

Answer 11

Interactions between alleles at different loci

-the expression of one gene affect the other

Instead of 9;3;5;1 you get 9;4;3

Question 12

How to test is an allele is recessive or dominate

Answer 12

Pure breeding

Breed new mutant (ob ob) with pure wild type (OB OB) if mutant shows up in F2 then mutant dominate

Question 13

Nomenclature

Answer 13

Genes are usaully named occording to their function

Question 14

Law of segregation

Answer 14

The two alleles for each gene seperate

Question 15

Law of independant assiortment

Answer 15

Alleles of genes on non-homologous chromosomes assort independently

-Alleles on different chromosomes have a 50% chance of ending up in the same gamete

Question 16

What does genetically linked mean

Answer 16

loci physically close together stay together during meiosis, autosomal linkage

Question 17

What’s wrong with mandels laws

Answer 17

they only considered segregation (genes on different chromosomes) which meant he could consider traits completely independent

Question 18

if b and vg genes are physically linked what does that mean for F1 generation

Answer 18

Most offspring b+ vg+ or b vg
With b vg+ and b+ vg being rare

Small area/ very close together so less chance of genotypes crossing over, most offspring match parents

Question 19

What is the recombination frequency ?

Answer 19

How often recombination/ crossing over occurs between genes.
Measure by fraction/ % of offspring inherit recombinant chromosomes

(recombinates / total offspring) x 100

Question 20

Compared to the x chromosome the y is what?

Answer 20

very reduced carries 200 genes including SDY (sex-determining region Y)

Question 21

What is SDY or TDF?

Answer 21

testies determinding factor, transcription factor that initiates male sex determination like testies (6-8 week)

Question 22

What are sex linked genes

Answer 22

genes on sex chromosomes

Question 23

X linked genes are what

Answer 23

father only pass to daughters who are carries not sons

carriers mothers have 50% pass on rate

Question 24

X inactivation

Answer 24

inactivation of 1 of 2 copies of x chromosome

• early in development one x chromo condenses into BARR BODY where genes are not expressed
• which is barr body made on cell by cell basis in first 100 cells