B2.7 Cell division and inheritance

Question 1

What do body cells divide by?

Answer 1

mitosis

Question 2

What do chromosomes contain?

Answer 2

genetic information

Question 3

Describe what happens when a body cell divides by mitosis

Answer 3

copies of genetic material are made.

then the cell divides once to form 2 genetically identical body cells

Question 4

When does mitosis occur?

Answer 4

during growth or to produce replacement cells

Question 5

What are sex cells called?

Answer 5

gametes

Question 6

How many sets of chromosomes do body cells have?

Answer 6

2

Question 7

How many sets of chromosomes do gametes have

Answer 7

1

Question 8

How many pairs of chromosomes does a human body cell have?

Answer 8

23

Question 9

Why do gametes only have 1 set of chromosomes (one copy of each chromosome)?

Answer 9

So when the sperm and egg fuse, you will get 46 chromosomes again.

Question 10

What are the reproductive organs?

Answer 10

testes and ovaries

Question 11

Which cells divide by meiosis to form gametes?

Answer 11

cells in reproductive organs -testes and ovaries

Question 12

What is meiosis?

Answer 12

A type of cell division which produces cells which have half the normal number of chromosomes (gametes)

Question 13

Describe what happens when a cell divides to to form gametes (meiosis)

Answer 13

Copies of the genetic information are made.

Then the cell divides twice to form 4 gametes, each with a single set of chromosomes.

Question 14

What happens when gametes join at fertilisation?

Answer 14

a single body cell with new pairs of chromosomes is formed. A new individual then develops by this cell repeatedly dividing by mitosis

Question 15

What are genetic diagrams?

Answer 15

biological models which can be used to predict the outcomes of crosses

Question 16

Most type of animal cells differentiate at an early stage whereas many plant cells retain the ability to….

Answer 16

differentiate throughout life.

Question 17

What are stem cells?

Answer 17

cells from adult bone marrow and human embryos which can be made to differentiate into many different types of cells. eg nerve cells

Question 18

Human stem cells have the ability to differentiate into…

Answer 18

any kind of human cell

Question 19

What may treatment with stem cells be able to do?

Answer 19

help conditions such as paralysis

Question 20

What are some advantages of using embryonic stem cells?

Answer 20

• Have the ability to develop into any kind of human cell unlike stem cells in adult bone marrow
• cure diseases and saving lives
• embryos used in research are only unwanted ones, which would probably just be destroyed

Question 21

What are some disadvantages of using embryonic stem cells?

Answer 21

• Killing potential human life
• Embryo can not give consent
• Some believe should use other sources of stem cells

Question 22

What are the cells of offspring produced by asexual reproduction produced by?

Answer 22

mitosis from the parent cells - they contain the same alleles as the parents so there’s so variation

Question 23

Why does sexual reproduction give a rise to variation?

Answer 23

Fertilisation occurs

which leads to the mixing of genetic information

one copy of each allele comes from each parent

Question 24

What are the sex chromosomes in females?

Answer 24

XX

Question 25

What are the sex chromosomes in males?

Answer 25

XY

Question 26

What is an allele?

Answer 26

a different form of the same gene

Question 27

What is a dominant allele?

Answer 27

expresses if just one copy of the allele is present

Question 28

What is a recessive allele?

Answer 28

An allele that controls the development of characteristics only if the dominant allele is not present

Question 29

What does DNA stand for?

Answer 29

deoxyribo nucleic acid

Question 30

What structure does DNA have?

Answer 30

a double helix structure

Question 31

What are chromosomes made up of?

Answer 31

large molecules of DNA

Question 32

Each gene code for a particular combination of amino acids which makes a...

Answer 32

specific protein

Question 33

What is DNA finger printing used to do?

Answer 33

identify individuals

Question 34

Some disorders are...

Answer 34

inherited

Question 35

Describe the genetic disorder - polydactyly

Answer 35

having extra fingers or toes- caused by a dominant allele of a gene and can therefore be passed on if only one parent has the disorder

Question 36

Describe the genetic disorder- Cystic fibrosis

Answer 36

-a disorder of cell membranes must be inherited from both parents. The parents may be carriers of the disorder without actually having the disorder themselves. It can be caused by a recessive allele of a gene and can therefore be passed on by parents, neither of whom has the disorder.

Question 37

Where are chromosomes found?

Answer 37

in body cells in the nucleus

Question 38

Why may embryos be screened?

Answer 38

To check for alleles that cause genetic disorders

Question 39

Give some reasons why people may be against embryo screening

Answer 39

- expensive - implies that people with genetic problems are 'undesirable' which could increase prejudice - May become a point where everyone wants to screen their embryos so they can pick the most desirable one 'designer babies' - rejected embryos are destroyed - embryos have a right to life

Question 40

Give some reasons why people are for embryo screening

Answer 40

- It will help stop people suffering - There are laws to stop it going too far - Treating disorders costs the government a lot of money so it reduces healthcare costs

Question 41

Describe the work of Mendel

Answer 41

Mendel cross bred pea plants. Discovered: - characteristics in plants are determined by 'hereditary units' - hereditary units can be dominant or recessive - hereditary units are passed on from both parents, one unit from each parent

Question 42

Why was the importance of Mendel's discovery not recognised until after his death?

Answer 42

Nobody knew anything about genes or DNA Mendel was not a well respected scientist

Question 43

What does it mean if an organism is homozygous?

Answer 43

it has 2 alleles for a particular gene the same. (eg AA)

Question 44

What does it mean if an organism is heterozygous?

Answer 44

2 alleles for a particular gene are different (eg Aa)

Question 45

What is a dominant allele shown by?

Answer 45

a capital letter

Question 46

What is a recessive allele shown by?

Answer 46

a small letter

Question 47

What does genotype mean?

Answer 47

combination of alleles you have (eg Bb)

Question 48

What does phenotype mean?

Answer 48

The characteristic you have (eg tall)

Question 49

From a family tree diagram, how can you tell if a disease is recessive (is not dominant)

Answer 49

if someone in the family carry the allele but are not sufferers

Question 50

Explain why offspring produced by sexual reproduction will look similar to its parents

Answer 50

because genes are passed from parents

Question 51

Explain why off spring produced by sexual reproduction will not be identical to either of its parents?

Answer 51

Chromosomes are from 2 parents Environmental factors may have been a mutation

Question 52

What is affected by cystic fibrosis?

Answer 52

cell membranes

Question 53

What is a gene?

Answer 53

a small section of DNA that codes for a particular combination of amino acids that make a specific protein

Question 53

What is the principle behind DNA finger printing?

Answer 53

every individual apart from identical twins has different DNA

Question 54

Why is it easier to clone plants than animals?

Answer 54

Most plant cells retain the ability to differentiate throughout life whereas most animal cells become specialised during the formation of an embryo

Question 55

Is polydactyl dominant or recessive?

Answer 55

dominant

Question 56

is cystic fibrosis dominant or recessive?

Answer 56

recessive

Question 57

What are the features of polydactyl?

Answer 57

extra fingers or toes

Question 58

What happens to the genetic material before the cell divides?

Answer 58

it replicates

Question 59

Why is it important that a sperm cell has 23 chromosomes?

Answer 59

as a sperm cell fuses with an egg cell fertilised egg cell now has 46 chromosomes- the full number

Question 60

give advantages of using stem cells from adult skin cells instead of from embryo cells

Answer 60

- no risk of damage to the embryo - adult can give consent for the removal of cells - skin cells are more accessible

Question 61

Explain why stem cells can be used to treat conditions such as paralysis?

Answer 61

because stem cells can be made to differentiate into nerve cells

Question 62

What are some differences between mitosis and meiosis

Answer 62

mitosis one cell division, meiosis 2 cell division cells produced by mitosis have 2 sets of chromosomes. cells produced by meioses have one set of chromosomes