B2.7 - Cell Division and Inheritance

Question 1

How are chromosomes in body cells found?

Answer 1

In pairs.

Question 2

Do body cells divide by mitosis or meiosis?

Answer 2

Mitosis.

Question 3

What do chromosomes contain?

Answer 3

Genetic Information.

Question 4

What happens when a cell divides by mitosis?

Answer 4

• copies of the genetic material are made

- then the cell divides once to form two genetically identical body cells.

Question 5

When does mitosis occur?

Answer 5

During growth or to replace cells.

Question 6

How many sets of chromosomes do body cells have?

Answer 6

Two.

Question 7

How many set of chromosomes do gametes have?

Answer 7

One.

Question 8

What type of cell division forms gametes?

Answer 8

Meiosis.

Question 9

What happens during meiosis?

Answer 9

-copies of the genetic information are made
-then the cell divides twice to form four
gametes, each with a single set of
chromosomes.

Question 10

What happens when gametes join in fertilisation?

Answer 10

A single body cell with new pairs of chromosomes is formed.

Question 11

How does a new person develop from fertilisation?

Answer 11

The cell formed by fertilisation divides by mitosis.

Question 12

How is differentiation different for plants and animals?

Answer 12

Most types of animal cells differentiate at an early stage whereas many plant cells retain the ability to differentiate throughout life.

Question 13

What is cell division restricted to in mature animals?

Answer 13

Repair and replacement.

Question 14

What are stem cells?

Answer 14

Cells from human embryos or adult bone marrow.

Question 15

How can stem cells be used?

Answer 15

They can be made to differentiate into many different types of cell, eg nerve cells.

Question 16

What can stem cells develop into?

Answer 16

Any kind of human cell.

Question 17

How can stem cells help with certain conditions?

Answer 17

They may be able to help conditions such as paralysis.

Question 18

How are offspring produced by asexual reproduction?

Answer 18

They are produced by mitosis from the parental cells. The offspring then have the same alleles as the parents.

Question 19

What is an allele?

Answer 19

Different forms of the same gene, eg blue eyes or brown eyes.

Question 20

What is a chromosome?

Answer 20

A structure of nucleic acids and protein found in the nucleus, carrying genetic information.

Question 21

What is a genotype?

Answer 21

The entire set of genes in an organism.

Question 22

What is a gene?

Answer 22

A small section of DNA.

Question 23

What does hetrozygous mean?

Answer 23

A person is heterozygous for a certain gene if they have two different alleles., eg one blue eye allele and one brown eye allele.

Question 24

What does homozygous mean?

Answer 24

An individual is homozygous for a certain gene if they have two identical alleles, eg two brown eye alleles.

Question 25

What is a phenotype?

Answer 25

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

Question 26

Why does sexual reproduction give rise to variation?

Answer 26

When gametes fuse, one of each pair of alleles comes from each parent.

Question 27

How is the sex of the offspring determined by sexual reproduction?

Answer 27

One of the 23 pairs of chromosomes carries the genes that determine sex. In females the sex chromosomes are the same (XX) in males the sex chromosomes are different (XY).

Question 28

What is a dominant allele?

Answer 28

An allele that controls the development of a characteristic when it is present on only one of the chromosomes.

Question 29

What is a recessive allele?

Answer 29

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

Question 30

What are chromosomes made up of?

Answer 30

Large molecules of DNA (deoxyribo nucleic acid) which has a double helix structure.

Question 31

What do genes do?

Answer 31

Each gene codes for a particular combination | of amino acids which make a specific protein.

Question 32

How an people be identified by their DNA?

Answer 32

Each person (apart from identical twins) has unique DNA. This can be used to identify individuals by DNA fingerprinting.

Question 33

What is Polydactyly, and how is it caused?

Answer 33

Having extra fingers or toes – is caused by a dominant allele of a gene and can therefore be passed on by only one parent who has the disorder.

Question 34

What is Cystic Fibrosis and how is it caused?

Answer 34

A disorder of cell membranes. It must be inherited from both parents, who may be carriers of the disorder without actually having it. It is caused by a recessive allele of a gene, therefore if two carriers have a child, it will potentially have Cystic Fibrosis.

Question 35

How can genetic disorders be caught early?

Answer 35

Embryos can be screened for certain alleles.