B2.7 Cell Division

Question 1

How many chromosomes do humans have?

Answer 1

46 (diploid)

Question 2

Define homologues

Answer 2

Specific number of chromosomes grouped in identical pairs

Question 3

Define allele

Answer 3

A different form of the same gene

Question 4

If an allele is recessive, how many are needed?

Answer 4

2

Question 5

If an allele is dominant, how many are needed?

Answer 5

1

Question 6

Define heterozygous

Answer 6

Different alleles

Question 7

Define homozygous

Answer 7

Identical alleles

Question 8

Define genotype

Answer 8

The genes that we have eg. Yy

Question 9

Define phenotype

Answer 9

The characteristic shown eg. colour of eyes

Question 10

What are the differences between mitosis and meiosis?

Answer 10

Mitosis divides once and produces 2 daughter cells

Meiosis divides twice and produces 4 daughter cells

Question 11

Where are stem cells found?

Answer 11

In early human embryos/ in tissues such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin and liver

Question 12

What are the 2 types of stem cell?

Answer 12

Adult and embryonic

Question 13

What are adult stem cells?

Answer 13

These are unspecialised cells that can develop into many (but not all) types of cells

Question 14

What are embryonic stem cells?

Answer 14

These are unspecialised cells that can develop into any type of cell

Question 15

Give an example of how stem cells have the potential to treat illness

Answer 15

Insulin-producing cells are made for patients that suffer from diabetes because they lose the function of their insulin-producing cells within the pancreas. Therefore, the stem cells produce insulin.

Question 16

What is the controversy regarding stem cells?

Answer 16

The argument for using embryonic stem cells are that the embryos used in research are normally unwanted ones from fertility clinics and that many people will be free from suffering and can be cured of diseases.

The argument against is that it’s immoral to destroy human life.

Question 17

Define gene

Answer 17

A gene is a section of DNA that codes for a specific protein

Question 18

Define chromosomes

Answer 18

They are long threads of DNA each made up of many genes that are found in the cell’s nucleus

Question 19

Define DNA

Answer 19

DNA molecules carry the genetic code that determines the characteristics of a living organism

Question 20

What are the advantages and disadvantages of genetic screening?

Answer 20

Advantages are that the parents can decide whether to keep or abort the baby and reducing the number of people living with cystic fibrosis reduces health care costs over time.

Disadvantages are that it puts the embryo and mother at risk as well as being very expensive!

Question 21

Define multicellular

Answer 21

An organism or part of one consisting of many cells

Question 22

What are gametes?

Answer 22

Sperm and egg that form sex cells

Question 23

What is the shape of a DNA molecule?

Answer 23

A double helix

Question 24

What is cystic fibrosis a disorder of?

Answer 24

Cell membranes

Question 25

What is meant by a ‘carrier’ of a genetic disease?

Answer 25

A carrier is an organism that has inherited a recessive allele for a genetic trait

Question 26

What are the features of polydactyl?

Answer 26

When an embryo is born with extra fingers or toes

Question 27

Why is it easier to clone plants than animals?

Answer 27

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