8J Genes

Question 1

Identify two resources that organisms compete for.

Answer 1

Food, water, space, mates, light (plants only)

Question 2

Define variation

Answer 2

Difference between individuals

Question 3

What is evolution?

Answer 3

A gradual change over time

Question 4

Why do organisms produce more offspring that is needed?

Answer 4

To increase the chance that some of them will survive

Question 5

What do we mean by the “fittest” organism will survive?

Answer 5

The best adapted organism will survive

Question 6

What animal did Darwin study when developing the theory of natural selection?

Answer 6

Galapagos finches

Question 7

What was different about these animals?

Answer 7

Beak shape and size

Question 8

Why were their differences important to Darwin’s theory?

Answer 8

Different beaks were better adapted to eat the different food available on different islands

Question 9

Define biodiversity

Answer 9

The variety of living things within an ecosystem

Question 10

State two ways we measure biodiversity

Answer 10

Number of different species, differences between individuals of same species

Question 11

Why do humans rely on plants?

Answer 11

Plants take in CO2 and produce O2, for food for us and the animals we eat, for medicines

Question 12

Why is a reduction in biodiversity bad for humans?

Answer 12

Less likely that we had all of the resources that we depend upon

Question 13

What is interdependence?

Answer 13

All organisms in a habitat rely on each other

Question 14

Why are food chains more stable in high biodiversity ecosystems?

Answer 14

Removal of one species is less likely to have a massive impact on the rest of the food web.

Question 15

What do we mean by the term “endangered species”?

Answer 15

When there are few individuals left of a species

Question 16

Define extinct

Answer 16

When a species has died out and there are no more left

Question 17

What is a mass extinction?

Answer 17

The extinction of many species all at once

Question 18

When was the last mass extinction?

Answer 18

65 million years ago

Question 19

State two natural causes of extinction.

Answer 19

Climatic heating and cooling, changes in sea level, asteroid impacts, disease

Question 20

State two ways that human activities cause extinction.

Answer 20

Hunting, habitat destruction, introduction of invasive species, over-exploitation of wildlife

Question 21

What is a gene bank?

Answer 21

A collection of seeds, sperm, eggs, embryos, blood and cuttings to preserve the genetic material of endangered plants of animals

Question 22

Why is the Northern white rhino described as extinct, even though there are two individuals still alive?

Answer 22

Both are females so cannot reproduce

Question 23

What did scientists use to create a cloned Pyrenean ibex?

Answer 23

A frozen sample of tissue and a Spanish Ibex

Question 24

In which part of the cell is an organism’s genetic material found?

Answer 24

Nucleus

Question 25

What does DNA stand for?

Answer 25

Deoxyribonucleic acid

Question 26

How many pairs of chromosomes do humans have?

Answer 26

23 pairs (46 chromosomes in total)

Question 27

What is a gene?

Answer 27

Short sections of DNA that code for proteins

Question 28

What shape is DNA?

Answer 28

Double helix

Question 29

What are the base pairs?

Answer 29

A and T, C and G

Question 30

Why is detergent added to the ground up fruit?

Answer 30

To break down the cell and nucleus membrane, to release the DNA

Question 31

What is used to separate DNA from a solution?

Answer 31

Ethanol – DNA is insoluble in ethanol so will form a separate layer

Question 32

Name the four scientists who discovered the structure of DNA.

Answer 32

Watson, Crick, Franklin, Wilkins

Question 33

When was the structure of DNA discovered?

Answer 33

1950s

Question 34

How was X-ray crystallography used to discover the structure of DNA?

Answer 34

It was used to photograph the double helix shape of DNA

Question 35

What did Erwin Chargaff contribute to the discovery of the structure of DNA?

Answer 35

Found out that DNA was made of base pairs – A, T, C and G

Question 36

How was the final model of DNA created?

Answer 36

Franklin’s x-ray photograph and Chargaff’s base pairs were used to build a model

Question 37

Why were only three scientists awarded a Nobel Prize for their discovery?

Answer 37

Franklin died before the prize was awarded

Question 38

Why did these four scientists have to collaborate to discover the structure of DNA?

Answer 38

They each contributed something different to the discovery

Question 39

What is the Human Genome Project?

Answer 39

A project to discover the exact sequence of base pairs in every gene in every chromosome in a human cell

Question 40

What is a gamete?

Answer 40

Sex cell, e.g. a sperm or egg

Question 41

Why do gametes have half a set of chromosomes?

Answer 41

So that when they join they have a full set

Question 42

How is a karyotype prepared?

Answer 42

Chromosomes are separated from the cell and spread out on a microscope slide

Question 43

Why is there variation amongst the offspring of two parents?

Answer 43

The alleles in each sperm or egg are completely random

Question 44

What is trisomy?

Answer 44

When three chromosomes are inherited instead of a pair

Question 45

What are the effects of trisomy 21?

Answer 45

Down’s syndrome

Question 46

Give an example of a genetic disorder not caused by trisomy.

Answer 46

Sickle cell anaemia, cystic fibrosis

Question 47

What is a carrier?

Answer 47

Someone who carries the allele for a disease but does not have the disease itself. They can pass it on to their children

Question 48

What is an inherited characteristic?

Answer 48

Characteristics that are inherited from parents through the genes

Question 49

Give an example of a human inherited characteristic.

Answer 49

Eye colour, blood type, freckles

Question 50

How many chromosomes does each parent pass on to their offspring?

Answer 50

Half a full set, e.g. 23 for humans

Question 51

Why do siblings look similar, but not identical?

Answer 51

They share some characteristics from each parent

Question 52

What happens to produce identical twins?

Answer 52

A fertilised egg splits to produce two foetuses

Question 53

Define what an embryo is.

Answer 53

An early stage of development of an animal, a small ball of cells

Question 54

Why are identical twins never exactly the same?

Answer 54

Environmental factors affect their appearance

Question 55

How are non-identical twins produced?

Answer 55

Two eggs, released at the same time, are fertilised by separate sperm

Question 56

Why do we use models of inheritance?

Answer 56

To predict the likelihood of inheriting certain genes

Question 57

What is an allele?

Answer 57

Different forms of the same gene

Question 58

Why is the brown fur allele described as dominant?

Answer 58

It is always expressed even if there is only one copy of the brown allele

Question 59

Why is the white fur allele described as recessive?

Answer 59

It is only expressed if both alleles are for white fur

Question 60

Why is it not possible to know the alleles of a brown mouse?

Answer 60

It may have two brown alleles, or one brown and one white allele

Question 61

How many possible combinations of alleles are there?

Answer 61

Three

Question 62

For the Punnett square above, what are the chances the mouse will be brown?

Answer 62

¾ or 75%

Question 63

Why is it more likely that a mouse will be brown than white?

Answer 63

Brown is the dominant allele, only one needs to be inherited to be expressed