Inheritance

Question 1

Define:
Gene
Allele
Genotype
Phenotype
Monohybrid

Answer 1

Gene - inherited instruction which codes for a polypeptide
Allele - alternate form of a gene. Can arise from mutation
Genotype - genetic constitution of an organism that determines characteristics
Phenotype - observable traits of an organism
Monohybrid cross - cross in which the allele of only one gene are inherited

Question 2

Monohybrid inheritance

Answer 2

HH + hh = 100% Hh offspring

Hh + hh = 50/50 Hh hh

Question 3

Test cross

Answer 3

Determines if an organisms is homozygous dominant or heterozygous
Whether 2 genes are linked or not
Alway cross with homozygous recessive

Question 4

Co-dominance

Answer 4

• When alleles of a gene share dominance of characteristics - both are expressed in the phenotype
• example of diagram is capital letters with smaller letters as powers and as the characteristic

Question 5

Autosomal

Answer 5

Not sex chromosome

Question 6

ABO blood groups

Answer 6

IA + IB are dominant to I0 ??/

Question 7

Dihybrid cross

Answer 7

Inheritance of two genes with 2 different alleles each on different chromosomes

Independent segregation = alleles on different chromosomes so can pass into gametes in any combo

Question 8

9:3:3:1

Answer 8

DD : Dr : Dr : rr

Question 9

Autosomal linkage

Answer 9

• non sex chromosomes
• if genes are on same chromosome it is assumed they are inherited together (linked and no crossing over)

Question 10

Sex - linked inheritance

Answer 10

• genes on sex chromosomes

Question 11

XX AND XY

Answer 11

XX = FEMALE
XY = MALE

Y = smaller so most genes on X. No homologous alleles present on Y.
Characteristics caused by recessive alleles have greater chance of appearing in males.

Question 12

Chi Squared

Answer 12

• assess if observed if significantly different from expected
• categorical raw values
• null hypothesis = no sig diff between O and E
• if calculated value is less than critical value then accept null.

Question 13

Epistasis

Answer 13

• polygenetic characteristics
• when alleles of one gene mask expression of another
• dominant = mask expression of alleles at second gene locus
• recessive - 2 recessive at one gene mask allies expression of another

Question 14

In genetic crosses, why are observed phenotypic ratios not the same as the expected ratios

Answer 14

-random fertilisation of gametes
-mutation/crossing over
-small sample size
-linked genes
-epistasis
-lethal genotypes

Question 15

Describe these phenotype frequencies:
- 1860, 580, 68,57

Answer 15

• larger numbers linked genes
• smaller numbers means a mutation has occurred which means they are random, not linked and not expected but onbserved.
• smaller numbers caused by crossing over

Question 16

Assumptions to why expected and observed are not the same?

Answer 16

• small sample size
• random fertilisation of gametes
• legthal genotypes

Question 17

Why is chi squared used

Answer 17

• to show if difference between observed and experceted is significant or not
• it’s CATEGORICAL DATA