4. Genetics

Question 1

What is meant by genome

Answer 1

All the genetic material of an organism

Question 2

What are chromosomes

Answer 2

Genetic structures that function in pairs
they are found in the nucleus of a cell
They are made up of genes and DNA

Question 3

What is a gene

Answer 3

A section of a chromosome that control a particular characteristic eg hair colour

Question 4

What is an allele

Answer 4

Different forms of the same gene e.g. gene for hair colour may have a brown hair allele, blond hair allele, black hair allele

Question 5

What is DNA

Answer 5

made up of nucleotides that are joined together by the sugar - phosphate back bone

Question 6

What are the 4 types of bases found on a nucleotide

Answer 6

A, T, G, C

Question 7

What base pairs occur between bases of nucleotides

Answer 7

A base pairs with T
G base pairs with C

Question 8

How does DNA work

Answer 8

DNA codes for the order of the amino acids in a protein
The base code is always in groups of 3 - known as the triplet code

Question 9

If a gene has 54 bases along its coding strand for a protein. How many amino acids make up the protein

Answer 9

1 amino acid -= 3 bases
54/3 = 18 amino acids

Question 10

What is the shape of DNA called

Answer 10

Double Helix

Question 11

What are the most common proteins DNA produce

Answer 11

Enzymes - which control the development of a cell

Question 12

What happens in mitosis

Answer 12

Mitosis is cell division to produce replacement cells, repair cells or for growth

Before division the chromosomes in nucleus make a complete copy of themselves
They line up at the middle of cell and then divide into 2 daughter cell
Each daughter cell has exactly the same number of chromosomes as the original (diploid cells)

Question 13

What is meiosis

Answer 13

Cell division that happens to produce gametes - sperm and egg cells
Before division chromosomes duplicate (double the number)
Involves 2 cell divisions
Produce 4 daughter cells that have half the genetic information as the original cell (haploid cells)

Question 14

What is independent assortment in meiosis

Answer 14

How the chromosomes separate the pairs of chromosomes is random so can lead to variation in the combination of each chromosome in each gamete

Question 15

Why is meiosis important

Answer 15

When the sperm and egg join at fertilisation it ensures that the diploid number of chromosomes (23 pairs) is restored

Question 16

What is meant by a dominant allele

Answer 16

The characteristic that the dominant allele codes for will be expressed even if only one allele is dominant - if the person is heterozygous or homozygous dominant

Question 17

What is meant by a recessive allele

Answer 17

The characteristic that the recessive allele codes for will ONLY be expressed if both alleles are recessive - homozygous recessive

Question 18

What is meant by heterozygous

Answer 18

Alleles are different e.g. Bb

Question 19

What is meant by homozygous

Answer 19

The alleles are the same eg BB, bb

Question 20

What is meant by genotype

Answer 20

The genetic combination of the pair of allele eg Bb

Question 21

What is phenotype

Answer 21

The feature/characteristic that the genotype will produce
eg. Bb genotype results in brown hair (phenotype)

Question 22

What is the name of the drawing you do too show a genetic cross

Answer 22

Punnett square

Question 23

What would be the outcome ratio if both parents are heterozygous eg Bb

Answer 23

Bb x Bb
gametes are B or b

Complete punnett square

Offspring - 1 BB, 2Bb, 1bb
Ratio 1:2:1
or 3:1 ratio have dominant feature

Question 24

What is a test cross

Answer 24

This is when you want to find out if the organism with the dominant characteristic is heterozygous or pure breeding (homozygous dominant)

Complete cross with a homozygous recessive (as know its genotype)

If all offspring are dominant featured then the parent is homozygous dominant
e.g BB x bb = all offspring Bb

If half of the offspring have the recessive feature then they are heterozygous
Bb x bb = 2Bb: 2bb

Question 25

What is a pedigree diagram

Answer 25

A type of family tree in which you can work out the genotype of people using information provided

Question 26

Who was Mendel

Answer 26

Mendel studied peas and developed the laws of genetics by doing crosses between different characteristics

Question 27

What causes Cystic Fibrosis

Answer 27

A recessive allele
parents could be carriers (heterozygous Cc) and pass the allele onto a child

Cc x Cc
1 CC, 2Cc and 1 cc - with the condition

Question 28

What causes Huntingtons Disease

Answer 28

A dominant allele
Person may already have children before know they have the condition

Can be heterozygous an still have condition

Question 29

What is haemophilia

Answer 29

A sex linked condition found on the X chromosome (recessive condition)
Males more likely to get condition as only inherit 1 X chromosome
XhY

Question 30

What is Downs Syndrome

Answer 30

Caused by a chromosome mutation
Person gets extra chromosome on pair 21
Have 47 rather than 46 chromosomes

Question 31

What is genetic screening

Answer 31

If a person knows a condition in family tree may wish to test to see if they have the condition

Common - used in diagnosing Downs Syndrome - doing an amniocentesis
Taking sample of amniotic fluid and growing the cells in it (from foetus)
Seeing if have 47 chromosomes

Ethical issues - person may then abort the child

Question 32

What is genetic engineering

Answer 32

Removing the gene from one organism and inserting into another organism

e.g. insulin
Removing insulin from chromosome using Restriction Enzymes
Cutting open plasmid DNA of bacteria using restriction enzyme
inserting gene into the plasmid
Placing the genetically modified plasmid into the host (bacteria)
They reproduce and all bacteria have the gene for making insulin

Question 33

What processes happen in downstreaming

Answer 33

Extraction
Purification
Packaging (of insulin)

Question 34

What is a bioreactor

Answer 34

The container that grow bacteria in to produce insulin - conditions monitored e.g. pH, oxygen , glucose
Surrounded by cooling jacket to remove heat released during respiration
Mixed with stirrer to keep bacteria in contact with food and ensure aerobically respiring