Inheritance, Variation and Evolution

Question 1

DNA

Answer 1

Deoxyribonucleic acid. The chemical that all of the genetic material in a cell is made up from. A polymer in the shape of a double helix

Question 2

Chromosomes

Answer 2

Chromosomes come in pairs and are really long structures that contain DNA

Question 3

A gene

Answer 3

Small section of DNA. Each gene codes for a particular sequence of amino acids which are put together to make a specific protein. Only 20 amino acids are used but they make up thousands of different proteins. Genes simply tell what order to put amino acids together

Question 4

Genome

Answer 4

The entire set of genetic material in an organism

Question 5

Sexual reproduction

Answer 5

Genetic information from two organisms (mother and father) is combined to produce offspring which are genetically different to either parent. Fusion of gametes (23 chromosomes from each parent) using meiosis

Question 6

Asexual reproduction

Answer 6

Only one parent so the offspring are genetically identical to that parent using mitosis

Question 7

Meiosis process

Answer 7

Before dividing the cell duplicates its genetic information and the chromosomes arrange themselves in pairs. The pairs line up in the centre of the cell and are then pulled apart so each new cell has only one copy of chromosomes, some from the father and some the mother. In the second division they lineup again in the centre and get pulled apart again. This results in 4 gametes each with only a single set of chromosomes in it. Each gamete is genetically different since the chromosomes get shuffled and each gamete only gets half of them at random

Question 8

After two gametes have fused during fertilisation what does the resulting new cell do

Answer 8

Divides by mitosis to make a copy of itself. Mitosis repeats many times to produce many new cells in an embryo. As the embryo develops these cells start to differentiate and make an organism

Question 9

What does meiosis do

Answer 9

Produces cells with half the normal number of chromosomes

Question 10

How many chromosomes are there in a human body cell

Answer 10

23 pairs. 22 are matched pairs which control your characteristics. The 23rd pair are labelled XY or XX. They decide your sex, males have XY and females have XX. There is a 50% chance of being male or female

Question 11

Alleles

Answer 11

Versions of genes

Question 12

Homozygous and heterozygous

Answer 12

Homozygous is when two alleles of a particular gene are the same and heterozygous is when they are different

Question 13

Genotype

Answer 13

The combination of alleles that you have, for example Dd

Question 14

Embryonic Screening

Answer 14

When a embryo inside the womb is tested to see if it has an inherited disorder from their parents who must either be carriers or have the disorder themselves

Question 15

Againts embryonic screening

Answer 15

Implies that people with genetic problems are ‘undesirable’- prejudice
May come to a point when everyone screens it to get the most desirble child eg. blue eyed, blond-haired, intelligent boy
Screening is expensive

Question 16

Variation

Answer 16

Differences within a species

Question 17

Gene mutation

Answer 17

A rare, random change in an organism’s DNA that can be inherited. Means a gene can be altered which produces a genetic varient (different form of a gene)

Question 18

Charles Darwin Theory of Evolution

Answer 18

Organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive. This idea is called ‘survival of the fittest’. The successful organisms that survive are more likely to reproduce and pass on the genes for the characteristics that made them successful to their offspring. Organisms that are less well adapted are less likely to survive and pass on their genes. Overtime beneficial characteristics become more common in the population and the species evolves.

Question 19

Speciation

Answer 19

Deveolpment of a new species through change in phenotype of organisms

Question 20

5 ways extinction can happen

Answer 20

The environment changes too quickly
A new predator kills them all
A new disease kills them all
They can’t compete with another (new) species for food
A catastrophic event kills them all

Question 21

Selective Breeding

Answer 21

When humans artificially select the plants or animals that are going to breed for their desirable characteristics and for their own benefit

Question 22

Drawback of selective breeding

Answer 22

Reduces the gene pool. The ‘best’ animals or plants will be closely related. This is inbreeding. There is more chance of organisms inheriting harmful genetic defects when the gene pool is limited. Also a problem if a new disease appears because there is no variation, if a disease can kill one of them it can kill all of them since they are closely related

Question 23

Genetic Engineering

Answer 23

Transferring a gene responsible for a desirable characteristic from one organism’s genome into another organism, so that it also has the desirable characteristic

Question 24

4 examples of genetic engineering

Answer 24

Bacteria to produce human insulin to treat diabetes
GM crops to improve quality of fruit and resistant to disease, insects
Sheep so milk can treat human diseases
Gene therapy, insert working genes into people with faulty genes (inherited disease)

Question 25

Fossils

Answer 25

Remains of organisms from many thousands of years ago, found in rocks. Provide evidence that organisms lived ages ago and can say how much an organism has evloved over time

Question 26

3 ways fossils form in rocks

Answer 26

Gradual Replacement by Minerals
Casts and Impressions
Preservation in Areas of No Decay

Question 27

‘Superbugs’

Answer 27

Bacteria that is resistant to most known antibiotics. An example is MRSA

Question 28

Carl Linnaeus classification

Answer 28

Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 29

Carl Woese three domain system

Answer 29

Archaea- primitive bacteria
Bacteria- true bacteria
Eukaryota- broad range of organisms including fungi

Question 30

Binomial System

Answer 30

Every organism is given its own two-part Latin name. First part refers to genus it belongs to and the second part the species. It’s used worldwide to ensure scientists around the world refer to a species by the same name to avoid confusion

Question 31

What are the four bases found in DNA

Answer 31

adenine (A), cytosine (C), guanine (G), thymine (T)

Question 32

Why does no one know how life began

Answer 32

Many early forms of life were soft-bodied and soft tissue tends to decay away completely so the fossil record is incomplete. Fossils may have also been destroyed by geological activity