Topic 3 + 4

Question 1

What happens in metaphase?

Answer 1

Chromosomes line up along the equator of the cell and become attached to the spindle fibers at the centromeres.

Question 2

How does meiosis produce cells that are genetically different ?

Answer 2

Through crossing over of chromatids and independent assortment of chromosomes

Question 3

What is genetic diversity?

Answer 3

The variation of alleles in the gene pool of a species

Question 4

How does the structure of sclerenchyma make them good for rope?

Answer 4

Sclerenchyma has thick lignin walls for strength and makes them waterproof.
It is flexible so do not break easily and light because are hollow.

Question 5

What are histones?

Answer 5

Proteins that DNA wraps around to form chromatin which makes up chromosomes

Question 6

Why do plants need magnesium ions?

Answer 6

For synthesis of chlorophyll

Question 7

What are the adaptations of an egg cell ?

Answer 7

1. Zona pellucida - a protective layer that sperm cell has to penetrate
2. Follicle cells - form a protective coating outside cell
3. Cytoplasm contains lipid droplets that are a food store for developing embryo.

Question 8

What is a niche?

Answer 8

The role of a species within its habitat including both biotic and abiotic interactions.

Question 9

What does the cell cycle consist of ?

Answer 9

Interphase which is a period of cell growth and DNA replication (G1, S and G2) then Mitosis

Question 10

How does the new three domain system classify organisms?

Answer 10

All organisms are placed into one of three domains which are above the kingdoms in the taxonomic hierarchy. The three domains are bacteria, archaea and eukaryote

Question 11

What is pluripotency ?

Answer 11

Ability of a stem cell to produce all the specialised cells in an organism but not extra embryonic cells

Question 12

What is an operon ?

Answer 12

A section of DNA that contains a cluster of structural genes that are transcribed together as well as control elements and sometimes a regulatory gene

Question 13

Give examples of X linked disorders colour

Answer 13

Haemophillia and colour blindness

Question 14

What is the function of the Golgi apparatus?

Answer 14

It processes and packages new lipids and proteins. it also makes lysosomes

Question 15

What does p stand for in p + q = 1?

Answer 15

The frequency of the dominant allele

Question 16

What is a loci?

Answer 16

Position of a gene on a chromosome

Question 17

Describe phase 3 of clinical trials

Answer 17

Testing the drug on thousands of patients and comparing it to existing treatment.
Split the patients randomly into two groups, one group gets new treatment and the other gets existing treatment

Question 18

Description and function of the amyloplast

Answer 18

A small organelle enclosed by a membrane.
Stores starch granules
Converts starch back to glucose for release when the plant requires it

Question 19

Define anatomical adaptations

Answer 19

Structural features of an organism’s body that increase its chance of survival

Question 20

Why is it important that gametes only have one set of chromosomes ?

Answer 20

So that the diploid number of chromosomes can be restored after fertilisation

Question 21

Why are seeds stored in dry and cold conditions?

Answer 21

Reduces enzyme activity, prevents germination of seeds, prevents microbial growth

Question 22

What is polygenic inheritance ?

Answer 22

There are multiple genes for a single characteristic on more than one locus. These genes interact. Usually show continuous variation.

Question 23

what is evolution?

Answer 23

The process by which the frequency of alleles in a gene pool changes over time as a result of natural selection.

Question 24

what is natural selection

Answer 24

It is the process by which individuals with a favourable phenotype are more likely to survive and pass on their alleles to their offspring.

Question 25

what does mutation in a species cause

Answer 25

it causes variation in a gene pool in a population

Question 26

what are the four mechanisms of evolution

Answer 26

1. gene flow - genes moving through migration e.g. migration
2. mutation e.g. changes in bases in DNA (genetic material)
3. genetic drift - change in gene pool due to random event
   4.natural selection have a better suited phenotype lead to change in frequency of alleles causing speciation