Bio Heredity

Question 1

Monohybrid inheritance

Answer 1

1 characteristic, 2 contrasting forms
Controlled by a single gene -> one pair of alleles, dominant or recessive

Question 2

Gene

Answer 2

Unit of inheritance on particular locus on a chromosome
Small segment of DNA, controls prod of a single polypeptide

Question 3

Alleles

Answer 3

Diff forms of same gene, occupying same relative positions on a pair of HCs

Question 4

Homologous chromosomes

Answer 4

Pairs, identical shapes sizes lengths, one from f one m parent
Same sequence of gene loci

Question 5

Phenotype

Answer 5

Observable traits
Influenced by genotype and environment

Question 6

Genotype

Answer 6

Genetic make-up
Homozygous: TT, tt
Heterozygous: Tt

Question 7

Genetic diagram

Answer 7

Parents phenotypes
Parents genotypes

Gametes

F1 generation genotypes
F1 generation phenotypes
Ratio of F1 generation phenotypes

Question 8

Codominance

Answer 8

Both alleles equally expressed in the heterozygous condition

Eg C^R C^R (red), C^RC^W (brown)
Eg blood groups in humans

Question 9

Sex determination alleles

Answer 9

Eggs X
Sperm X or Y

Question 10

Multiple alleles

Answer 10

Gene for trait exists in more than 2 alleles
Eg ABO human blood type
I^A(d), I^B (d), I^O (r)

Question 11

Discontinuous variation

Answer 11

• a few phenotypes
• controlled by one or a few genes
• genes do not show additive effect
• not affected by enviro
  Eg, either double or single eyelids

Question 12

Continuous variation

Answer 12

• a range of phenotypes
• controlled by many genes
• genes show additive effect
• effected by enviro
  eg skin colour range betw dark and fair

Question 13

Mutations

Answer 13

• errors during replication of gene/ chromosome

Question 14

Chromosome mutation

Answer 14

• change in structure / number
• eg Down syndrome

Question 15

Gene mutation

Answer 15

• change in DNA structure
• prod variation due to new alleles
• eg albinism and sickle cell anaemia

Question 16

Down syndrome

Answer 16

47 chromosomes instead of 46
Extra of C21

Question 17

Albinism

Answer 17

Gene mutation of recessive allele
Absence of pigment melanin

Question 18

Sickle cell anaemia

Answer 18

• Gene mutation in haemoglobin prod gene (recessive)
• sickle shaped -> lower O2 carrying capacity, clump tgt // v SA:V ratio, v rate of O2 diffing, v aerobic resp, v energy
• more resistant to malaria

Question 19

Mutagenic agents

Answer 19

Radiation:
- UV light, X-ray
- alpha and beta rad
- gamma rays

Chemicals
- mustard gas
- formaldehyde
- LSD

Question 20

Variation

Answer 20

• crossing over P1
• independent assortment M1
• mutation : new alleles for natural selection to act on

Impt to help orgs survive in changing enviro

Question 21

Natural selection

Answer 21

• best adapted (favourable characteristics) orgs in pop survive and repro, pass genes to next gen
• selects: more disease resistant, better adapted

Question 22

Natural selection vs artificial 4

Answer 22

Result of gene mutations / from human manipulation
Brought abt by enviro conditions change / humans select orgs w desired traits to repro
Very slow process / relatively faster
May be pos or neg/ always advantageous to man