Genetics and Cell Division

Question 1

What is DNA made up of?

Answer 1

Nucleotides containing bases. DNA has four different bases: Adenine (A), Cytosine (C), Guanine (G), Thymine (T)

Question 2

What does Adenine (A) bond to?

Answer 2

Thymine (T)

Question 3

What does Cytosine (C) bond to?

Answer 3

Guanine (G)

Question 4

What does Guanine (G) bond to?

Answer 4

Cytosine (C)

Question 5

What does Thymine (T) bond to?

Answer 5

Adenine (A)

Question 6

Why does A bond with T and C bond with G?

Answer 6

These pairs are complementary bases. They join together because they complement each other in shape - this is called complementary base pairing.

Question 7

What is the name given to the double-stranded structure of DNA?

Answer 7

Double helix

Question 8

How many different bases are there in DNA?

Answer 8

4

Question 9

Give the names of the bases in DNA.

Answer 9

Adenine, cytosine, guanine, thymine

Question 10

How do the strands of DNA stay together?

Answer 10

Each base forms hydrogen bonds to a base on the other strand.

Question 11

What is complementary base pairing?

Answer 11

This is when pairs of complementary bases join together. A pairs with T and C pairs with G.

Question 12

What is a gene?

Answer 12

A section of DNA that codes for a specific protein.

Question 13

What determines the order of amino acids in a protein?

Answer 13

The order of bases in the gene.

Question 14

What is needed to make proteins?

Answer 14

RNA

Question 14

In RNA there is no thymine (T). What base replaces it?

Answer 14

Uracil (U)

Question 15

*Why does a copy of a gene need to be made for protein synthesis? *

Answer 15

Because the DNA molecule containing the gene is in the nucleus and is too big to leave the nucleus. But protein synthesis takes place in the cytoplasm, so a copy of the gene that is smaller and can leave the nucleus needs to be made.

Question 16

What does the ‘m’ in mRNA stand for?

Answer 16

Messenger

Question 17

In RNA, which base is complementary to adenine?

Answer 17

Uracil

Question 18

Give the mRNA sequence that would be complementary to the DNA sequence: ATTGCGCA

Answer 18

UAACGCGU

Question 19

What is a triplet?

Answer 19

Three bases in a row e.g. ACC

Question 20

What do three bases in a row code for?

Answer 20

One amino acid

Question 21

What is a mutation?

Answer 21

A change to the base sequence of DNA

Question 22

How many bases code for one amino acid?

Answer 22

Three

Question 22

Mutations happen spontaneously, but how frequently they happen can be increased by what?

Answer 22

Mutagenic agents - factors that increase mutations, e.g. UV radiation in sunlight.

Question 23

What can a change in amino acid cause?

Answer 23

A different protein to be formed

Question 24

*What are mutations?*

Answer 24

Changes to the base sequence of DNA

Question 25

*What do mutagenic agents do?*

Answer 25

Increase the frequency of mutations.

Question 26

Where is DNA found?

Answer 26

In chromosomes

Question 27

What does each side of the 'X' referred to as?

Answer 27

A chromatid and the bit in the middle where they are attached is called the centromere

Question 28

How many pairs of chromosomes do humans have?

Answer 28

23 pairs (46 in total)

Question 29

How are human chromosomes found?

Answer 29

In pairs

Question 30

*Where is most DNA found in a eukaryotic cell?*

Answer 30

In the nucleus

Question 31

*How many homologous pairs of chromosomes do human cells have?*

Answer 31

23

Question 32

*Are homologous pairs of chromosomes identical. Explain your answer.*

Answer 32

No. with the exception of the sex chromosomes, they are the same size and carry the same genes but they usually have different alleles

Question 33

*What is a chromatid?*

Answer 33

An identical copy of a chromosome

Question 33

Cells divide by _____ to replace the damaged cells.

Answer 33

Mitosis

Question 34

*What is the name of the region where two identical chromatids are joined?*

Answer 34

Centromere

Question 35

Interphase

Answer 35

Before the cell starts to divide, every DNA molecule (each chromosome) must replicate so that each new cell has a full copy of the DNA. The new molecule remains attached to the original one at the centromere.

Question 36

All offspring are _____ _______ to each other and to the parent when mitosis occurs.

Answer 36

Genetically identical

Question 37

Prophase

Answer 37

Mitosis can now begin. Each DNA molecule becomes supercoiled and compact. Each chromosome can now be seen with a light microscope and appears as two chromatids lying side by side, joined by the centromere (i.e. X-shaped)

Question 38

Metaphase

Answer 38

The nuclear membrane breaks down and the chromosomes line up along the equator (middle) of the cell.

Question 39

Anaphase

Answer 39

The centromeres split and the chromatids separate and are dragged to opposite ends of the cell.

Question 40

Telophase

Answer 40

A nuclear membrane forms around each set of chromatids (exact copies of the original chromosomes) and the cytoplasm divides.

Question 41

*Give three uses of mitosis.*

Answer 41

Growth, repair and asexual reproduction

Question 41

*Do the homologous pairs separate in mitosis?*

Answer 41

No (the chromatids separate)

Question 42

*Why is DNA replicated before cell division can occur?*

Answer 42

So each new cell has a full copy of the DNA

Question 43

*How many cells are produced when a cell divides by mitosis?*

Answer 43

Two

Question 44

Sexual reproduction creates _______ in a population.

Answer 44

Variation

Question 45

Gametes are ______

Answer 45

Haploid

Question 46

During fertilisation the nuclei of the gametes join together to form a ______.

Answer 46

Zygote

Question 47

Zygotes are _____

Answer 47

Diploid

Question 48

*How many cells are produced when a cell divides by meiosis?*

Answer 48

Four

Question 48

*How many cell divisions are there in meiosis?*

Answer 48

Two

Question 48

*Are gametes haploid or diploid?*

Answer 48

Haploid

Question 48

The zygote grows by simple cell division (mitosis) to form the _______.

Answer 48

Embryo

Question 49

*Where in the human body does meiosis occur?*

Answer 49

In the testes or ovaries