DNA and cell division

Question 1

What is a genome?

Answer 1

the entire DNA (genetic information) of an organism

Question 2

What is a gene?

Answer 2

a section of DNA coding for a specific protein

Question 3

What is a chromosome?

Answer 3

A single strand of DNA found in the cells’ nucleus

Question 4

Where are genes found in the cell?

Answer 4

on the chromosomes

Question 5

Where are chromosomes found in the cell?

Answer 5

in the nucleus

Question 6

What are the three components of a nucleotide?

Answer 6

phosphate, (deoxyribose) sugar and nitrogenous (or organic) base

Question 7

What are the four organic (nitrogenous) bases in DNA?

Answer 7

Adenine, Thymine, Cytosine and Guanine

Question 8

What makes up the backbone of a DNA strand?

Answer 8

Sugar and phosphate groups - repeating

Question 9

How do the organic (nitrogenous) bases pair in DNA?

Answer 9

Adenine with Thymine and Cytosine with Guanine

Question 10

Describe the shape of a DNA strange

Answer 10

Coiled to form a double helix

Question 11

Give three differences between the structure of DNA and RNA

Answer 11

RNA is single stranded and DNA is double stranded.
RNA contains Uracil instead of Thymine.
The sugars are different (RNA contains ribose, DNA contains deoxyribose)

Question 12

Describe the steps in transcription

Answer 12

DNA helicase uncoils the DNA and separates the two strands.
RNA nucleotides are attracted to the complementary bases on the template strand of DNA (Uracil pairs with Adenine).
RNA polymerase forms bonds between the nucleotides.
mRNA molecule separates from DNA and leaves the nucleus.
DNA strands are attracted to each other again and recoil.

Question 13

Describe the steps in translation

Answer 13

mRNA binds with ribosome, with two codons (triplets of bases) in place.
tRNAs with complementary anticodons are attracted to the mRNA.
tRNAs have attached the amino acid corresponding to the codon.
Ribosome catalyses the reaction to join the two amino acids together.
First tRNA leaves and the mRNA moves through the ribosome so the next codon is in place.
A tRNA with the correct anticodon is attracted and the amino acid is bound to the growing chain.
This continues until the end of the mRNA is reached.

Question 14

What is the purpose of transcription?

Answer 14

Copying a gene as RNA, so that it can leave the nucleus and travel to the ribosome

Question 15

What is the purpose of translation?

Answer 15

To make the protein coded for by a particular gene (RNA)

Question 16

What is the function of mitosis?

Answer 16

To produce genetically identical daughter cells for growth, repair of tissue and asexual reproduction

Question 17

What happens to the chromosomes in mitosis?

Answer 17

Chromosomes line up at the centre of the cell and the copies separate, moving to the edges of the cell before cell division occurs

Question 18

Describe the key features of the cells produced in mitosis

Answer 18

Two daughter cells with a full (diploid) set of chromosomes, genetically identical to original cell

Question 19

What is the function of meiosis?

Answer 19

To produce genetically varied gametes

Question 20

What happens to the chromosomes in meiosis?

Answer 20

Division 1: pairs of chromosomes line up at the centre of the cell and separate, one chromosome moving to either end before cell division.
Division 2: individual chromosomes line up at the centre of the cell and the copies separate, moving to the edges of the cell before division occurs

Question 21

Describe the key features of the cells produced in meiosis

Answer 21

Four daughter cells with one of each chromosome (haploid), half the genetic information of the original cell.
Each cell has a different combination of chromosomes

Question 22

What causes genetic variation in offspring from the same parents?

Answer 22

Meiosis produces genetically different cells. Random fusion of gametes from mother and father

Question 23

What are the differences between mitosis and meiosis?

Answer 23

Mitosis produces 2 daughter cells, meiosis 4.
Mitosis involves one cell division, meiosis 2.
Mitosis produced dipolid cells, meiosis produces haploid cells.
In mitosis, the daughter cells are genetically identical to both each other and the original cell, in meiosis they are genetically different.
Mitosis is for growth, repair and asexual reproduction, meiosis produces gametes for sexual reproduction.

Question 24

What is meant by a diploid cell?

Answer 24

Contains pairs of chromosomes (so the cell has two copies of each gene)

Question 25

What is meant by a haploid cell?

Answer 25

Contains one of each chromosome (only one copy of each gene)

Question 26

What is the diploid number in humans?

Answer 26

46

Question 27

What is the haploid number in humans?

Answer 27

23

Question 28

What are the causes of variation (differences) between individuals of the same species?

Answer 28

genetic differences, the environment or a combination of both

Question 29

What is a mutation?

Answer 29

a change in the sequence of bases in DNA

Question 30

How does a mutation result in a changed characteristic?

Answer 30

it may result in a changed amino acid sequence in a protein, which can alter the shape (and therefore the function) of the protein

Question 31

Describe the possible effects of a mutation on a phenotype (characteristic)

Answer 31

Many mutations have no effect.
Some have a small effect and very few have a large effect.
The effect may be beneficial (result in a new, useful trait) or may be harmful (a protein may no longer function)

Question 32

Exposure to two things can increase the rate of mutation. What are they?

Answer 32

Ionising radiation (e.g. gamma rays or x-rays) or chemicals (mutagens).

Question 33

What is the name used to describe chemicals which cause mutations leading to cancer?

Answer 33

Carcinogens