Unit 2 KA 3 ✓

Question 1

What are the costs of Sexual reproduction? (2)

Answer 1

Sexual reproduction disrupts the successful parent genomes - only half of their DNA is passed on to offspring, instead of all.
Half the population (males) cannot directly produce offspring.

Question 2

What are the benefits of Sexual reproduction?

Answer 2

There is increased genetic variation which allows the population to adapt better to changes. The species has a better chance of surviving changing selection pressures

e.g. If offspring are more varied genetically, it would be less likely a disease would kill off all of them

Question 3

Asexual Reproduction -

What is Vegetitive cloning?

(Vegetitive propogation)

Answer 3

Vegetitive cloning results in all offspring being genetically identical to the original parent plant

e.g. Plantlets, bulbs, runners and tubers

Question 4

Asexual reproduction -

What is Parthogenesis?

Answer 4

Parthogenesis is reproduction from a female gamete without fertilisation.
Usually occurs in cooler climates disadvantageous to parasites or regions of lower parasite density

Question 5

What are the costs of Asexual reproduction?

Answer 5

Organisms have less genetic diversity than sexually reproducing organisms, so they are less able to adapt to a changing environment or selection pressures

Question 6

How is variation achieved in asexually reproducing populations?

Answer 6

Variation is achieved through mutations (during cell division) and horizontal gene transfer

Question 7

What is Horizontal gene transfer?

Answer 7

Horizontal gene tranfer is where genetic information is passed between prokaryote organisms (via a plasmid) of the same generation, allowing for faster evolutionary change as mutated genes can be spread

NOTE: A prokaryote is an organism whose cells lack a nucleus (Bacteria)

Question 8

What are the benefits of Asexual reproduction?

Answer 8

More offspring can be reproduced than with sexual reproduction because every member of the population can produce offpsring.
The whole successful genome is passed onto the offspring, an advantage in narrow, stable niches or when re-colonising a disturbed habitat.

Question 9

What is an organisms Niche?

Answer 9

A niche is the role an organism plays in its environment

Question 10

What is Meiosis?

Answer 10

Meiosis is the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte.

NOTE: A gametocyte is a germaline cell (from higher)

Question 11

What is a Homologous chromosomes?

(Homo- the same)

Answer 11

Homologous chromosomes are chromosomes of the same size, centromere position, gene sequence and loci

(loci - location)

Question 12

What are Linked genes?

Answer 12

Linked genes are those on the same chromosome, near each other

Question 13

What is Meiosis I?

Answer 13

Meiosis I is when a pair of homologous chromosomes is paired up and then split into two daughter cells

Question 14

What is Meiosis II?

Answer 14

Meiosis II is when sister chromatids are seperated and four haploid gametes are produced

Question 15

What is Chiasmata?

Answer 15

Chiasmata is the point of contact between non-sister chromatids of a homologous pair

Question 16

Meiosis I -

What is Crossing over?

(At Chiasmata)

Answer 16

Crossing over at chiasmata is when sections of DNA are exchanged producing recombinant chromosomes - this increases genetic variation

NOTE: Linked genes are more likely to move together during cross over

Question 17

Meiosis I -

What is Independent assortment?

Answer 17

Independent assortment is when the homologous chromosome pairs seperate irrespective of maternal or paternal origin

NOTE: Irrespective means “without considering”

Question 18

In humans,

What is Homogametic?

(Homo- the same)

Answer 18

In humans females are homogametic as they have XX chromosomes

Question 19

In humans,

What is Heterogametic?

(Hetero - the same)

Answer 19

In humans males are heterogametic as they have XY chromosomes

Question 20

What is the SRY gene?

Answer 20

The SRY gene is a gene on the Y chromosome of most mammals. It determines the development of male characteristics

Question 21

What is a Sex-linked gene?

Answer 21

A sex-linked gene is a gene which exists on the X chromosome but not on the much shorter Y chromosome. So in males, sex-linked genes are always expressed

Question 22

What is X chromosome inactivation?

Answer 22

X chromosome inactivation occurs in females. One of the two X chromosomes present in each cell is randomly inactivated early in development. This prevents a double dose of gene products and ensures carriers are less likely to be affected by harmful mutations

Question 23

What is a Hermaphrodite?

Answer 23

A hermaphrodite is a species where each individual has functioning male and female reproductive organs and can produce both male and female gametes to exchange with a partner

Question 24

Which factors can cause an organism to change sex after birth? (3)

Answer 24

• Size
• Competition
• Parasitic infection