Variation + DNA (paper 2)

Question 1

Differences in the characteristics of individuals in a population is called
variation and may be due to differences in:

Answer 1

• the genes they have inherited (genetic causes)
• the conditions in which they have developed (environmental causes)
• a combination of genes and the environment.

Question 2

usually what is the range of variation within a species

Answer 2

there is usually extensive genetic variation within a population of a species

Question 3

what do all variants arise from

Answer 3

mutations

Question 4

do mutation have an effect on its phenotype

Answer 4

most have No effect and some *influence** phenotypes , very few determine phenotype

Question 5

what is the phenotype

Answer 5

the physical characteristic of an organism which occurs as a result of its genes

Question 6

What are mutations, and how often do they occur?

Answer 6

Mutations occur continuously

Question 7

How and how often can a mutation lead to the evolution of a species in response to environmental changes?

Answer 7

• Very rarely a mutation will lead to a new
  phenotype
• If the new phenotype is suited to an environmental change it
  can lead to a relatively rapid change in the species

Question 8

species definition

Answer 8

individuals that share many characteristics and can reproduce to make fertile offspring

Question 9

describe the 4 key characteristics of a genetic source of variation

Answer 9

• some characteristic are inherited from our parents
• these characteristics are determined by our inherited genes
• our genes control the development of our characteristics
• each characteristic is controlled by a single gene

Question 10

what is the cause of environmental cause of variation

Answer 10

some characteristics can be altered and changed by lifestyle choices

Question 11

what is continuous variation

Answer 11

these characteristics show a range of many intermediates between 2 extremes

Question 12

what is discontinuous variation

Answer 12

different characteristics with no intermediates between them

Question 13

how is continuous data often represented

Answer 13

histogram with a range of characteristics divided into different classes

Question 14

how is discontinuous data often represented

Answer 14

bar chart

Question 15

what does DNA stand for

Answer 15

Deoxyribonucleic acid

Question 16

what is genetic material in the nucleus of a cell composed of

Answer 16

a chemical called DNA

Question 17

describe the structure of DNA

Answer 17

• is a polymer - large molecule made up of repeating subunits = nucleotides
• made of 2 strands which spiral round = double helix

Question 18

what does DNA contain

Answer 18

chromosomes

Question 19

gene definition

Answer 19

• A gene is a small section of DNA on a chromosome that codes for a specific sequence of amino acids to make a specific protein
• this protein determines a characteristic or trait

Question 20

what does a gene do

Answer 20

Each gene codes for a particular sequence of amino acids, to make a specific protein

Question 21

what is the genome of an organism

Answer 21

entire genetic material of that
organism.

Question 22

why will genomes be of great importance in the future

Answer 22

whole human genome has now been studied and this will
have great importance for medicine in the future.

Question 23

how many nucleotide make up DNA

Answer 23

4 different nucleotides

Question 24

what does each nucleotide consists of

Answer 24

a common sugar and phosphate group with one of 4 different basses attached to the sugar

Question 25

what are the 4 bases found in DNA

Answer 25

A, T, C, G

Question 26

what do the long polynucleotide stands of DNA consist of

Answer 26

- **alternating sugar** and **phosphate** sections - attached to each sugar is one of the 4 bases

Question 27

what happens in complementary base pairing

Answer 27

complementary strdans of the double helix: - **C** is always linked to a **G** on the opposite strand - **T** to **A**

Question 28

what codes for a particular amino acid

Answer 28

a sequence of **3 consecutive bases**

Question 29

what is the effect the order of the bases have on an amino acid

Answer 29

order of bases controls the **order** in which **amino acids are assembled** to produce a **particular protein**.

Question 30

what is a locus

Answer 30

the position of a gene on a particular chromosome

Question 31

allele definition

Answer 31

an alternative form of a **gene** that codes for the **different variation** of a **specific trait**

Question 32

describe the process of protein synthesis

Answer 32

Stage 1 (in nucleus): **Transcription**: 1. **base sequence** of the gene is **copied** into a complementary **template** molecule called **mRNA** 2. mRNA is a **single-stranded** molecule 3. mRNA passes out of nucleus (is smaller than DNA, able to pass out of nucleus) into the **cytoplasm** **Translation**: 4. mRNA molecule attaches to a **ribosome** 5. **amino acids** brought to ribosome on **carrier molecules / tRNA** 5. ribosome reads **triplets of bases** on the mRNA and **chemically join** together the **correct amino acids** in the **correct order** 6. one protein chain is complete it now **folds** up to form a **unique shape** 8. the unique chape enables the protein to carry out its **specific function**

Question 33

what are functions a protein cab do

Answer 33

- **enzymes - **hormones** - **forming structures** in the body such as *collagen**

Question 34

how often do mutations occur in the DNA

Answer 34

continuously

Question 35

what are mutations

Answer 35

**alterations** to the **base sequence** in the DNA

Question 36

what is the effect mutations have on a protein

Answer 36

- most do not alter the protein - or only alter it slightly but appearance or function is unchanged

Question 37

what are the 4 types of point mutations

Answer 37

- substitution : ATG ---> ACG - insertion: ATG --> ATCG - deletion: ATG --> AG - inversion: ATG --> AGT

Question 38

what effect coulf a mutation have on a protein

Answer 38

- change in base = **different amino acid** = change **shape of protein** - dramatic effect: - **active site** of an enzyme may change shape (no longer **complementary** --> can no longer attach to the **substrate** - if mutation changes shape of **structural protein** (collagen) then it may **lose its strength**

Question 39

non coding DNA =

Answer 39

DNA that does not code for a protein, instead **turns genes on and off**

Question 40

where contains non-coding DNA

Answer 40

chromosomes

Question 41

what are non-coding DNA sometimes called

Answer 41

introns

Question 42

what are sections of DNA that code for protein called

Answer 42

exons

Question 43

of mutations occur in non-coding section of DNA this can:

Answer 43

- **prevent** some **genes** being switched **on** = protein **not made** - **prevent** some **genes** being switched **off** = protein **made continuously** - variations in these areas of DNA may affect how **genes are expressed**