MODULE 5: Heredity

Question 1

External Fertilisation Example

Answer 1

Frogs: Males do not require a penis. Eggs are fertilised by male as they leave the female’s body. Amplexus process.

Question 2

External Fertilisation Advantages

Answer 2

1. Many Clones
2. Can quickly colonise habitats
3. Well suited to aquatic environments due to availability of water

Question 3

External Fertilisation Disadvantages

Answer 3

1. Many gametes required to ensure reproductive success
2. Lower rate of reproductive success
3. Water essential for sperm to swim and prevent from drying out -Challenging in terrestrial environments.
4. External stimuli needed to initiate release of gametes. (Temperature, Time of year, moon cycles and courtship rituals)

Question 4

Internal Fertilisation Example

Answer 4

Literally any animal - Use of penis further increases reproductive success.

Question 5

Internal Fertilisation Advantages

Answer 5

1. Greater reproductive success
2. Less gametes required

Question 6

Internal Fertilisation Disadvantages

Answer 6

1. Slower (longer gestation period)
2. Fewer offspring

Question 7

Mitosis Stages

Answer 7

PROPHASE
Chromosomes condense & become visible
Centrioles move to opposite sides of nucleus
Nuclear membrane breaks down
Centrioles form spindle fibres between the two poles

METAPHASE
Chromosomes align at an equatorial plane of cell
Spindle fibres attach to centromeres of chromosomes

ANAPHASE
Spindle fibres contract splitting the centromeres and separating sister chromatids
The separated chromosomes are pulled to opposite poles.

TELOPHASE
Nuclear membrane reforms around the two sets of chromosomes
Spindle fibres disappear
Chromosomes become longer and thinner

Creates Diploid Cell (2n)

Question 8

Meiosis Stages

Answer 8

1. Same as Mitosis except happens twice.
2. Creates Haploid cell (n)
3. Independent assortment in Metaphase
4. Crossing over in Metaphase
5. Random Segregation in Anaphase

Question 9

mRNA funciton

Answer 9

1. Messenger RNA
2. Carries DNA code into the cytoplasm to the ribosome.

Question 10

tRNA funciton

Answer 10

1. Transfer RNA
2. Carries amino acids from the cytoplasm to the ribosome to attach its complementary base pair codons on the mRNA strand to create a peptide chain.

Question 11

Co-dominance

Answer 11

Neither allele is dominant. Both alleles are expressed in the phenotype, this pattern of inheritance is referred to as codominance.
EXAMPLE: Roan Cattle. Red (RR) and white cattle (WW) can produce roans (RW).

Question 12

Incomplete Dominance

Answer 12

Neither allele masks the phenotypic expression of the other. There is a blend/mix of traits.
EXAMPLE: SnapDragon flower offspring mix colours of parents.

Question 13

Sex-linked alleles

Answer 13

Humans relate to genes on the X chromosome.
Males are more prone to sex-linked conditions as they only require one affected X chromosome, while female require two affected X chromosomes. Females that have one affected X chromosome and one unaffected X chromosome are called carriers.
EXAMPLE: Haemophilia - blood clotting disorder caused by recessive allele (h)

Question 14

Multiple alleles

Answer 14

Multiple alleles is where there is more than one dominant allele. In blood types, the IA and IB are both dominant, while the i allele is recessive.

Blood type:
A - IA, IAi
B - IB, IBi
AB - IAIB
O - ii