Topic 6

Question 1

What is DNA

Answer 1

A polymer made of two strands colied making a double helix. The polymers are made up of lots of repeating units called nucleotides

Question 2

What is a gene

Answer 2

A small section of DNA found on chromosomes, each codes for a particular sequence (what order) of amino acids which are put together to make a specific protein. Only 20 amino acid are used.

Question 3

What is a genome

Answer 3

Entire set of genetic material in an organism.

Question 4

Hhy is understanding the human genome important

Answer 4

Allows scientists to identify links to different diseases (which ones are inherited). It can also trace migration

Question 5

What does each nucleotide consist of

Answer 5

A sugar, a phosphate group and one ‘base’. These form a backbone to the DNA strands. They are complementary bases with C-G or A-T which decides the order of amino acids. Each amino acid is coded for by a sequence of three bases in the gene.

Question 6

What is mRNA and ribosomes effect of protein synthesis

Answer 6

Molecule which gets code from DNA to ribosomes. Proteins are synthesised on ribosomes, according to a template. Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order.

Question 7

Functions of protiens

Answer 7

Enzymes
Hormones
Structral Protiens

Question 8

What do parts of DNA that don’t code protien effect

Answer 8

Some of these non-coding parts switch genes off and on so they control wether or not a gene is expresses.

Question 9

What is the structure of a completed protin chain

Answer 9

When the protein chain is complete it folds up to form a unique shape. This unique shape enables the proteins to do their job as enzymes, hormones or forming structures in the body such as collagen.

Question 10

How do mutations occur

Answer 10

Mutations occur continuously. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.

Question 11

How does mutations effect enzymes

Answer 11

A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.

Question 12

What are different types of mutations

Answer 12

Insertions - when a new base is inserted (may have a knock-on effect)
Deletions - random bases deleted from DNA base sequence
Substitutions - random base is changed

Question 13

What does the father pordice is sexual reproduction

Answer 13

Gametes by meiosis

Question 14

What is exual reproduction

Answer 14

Involves the fusion of male and female gametes. Because there are two parents, the offspring contain a mixture of their parent’s genes.

Question 15

What does sexual reproduction lead to

Answer 15

sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.

Question 16

What does asexual reproduction involve

Answer 16

Asexual reproduction involves only one parent and no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.

Question 17

What is mitosis

Answer 17

An ordinary cell makes a new cell by dividing in two

Question 18

What are gametes

Answer 18

They only have one copy of each chromosome so that when gamete fusion takes place, you get the right amount of chromosomes agian.

Question 19

how meiosis halves the number of chromosomes in gametes

Answer 19

• first the cell duplicates its genetic information forming two armed chromosomes (each arm being an exact copy of the other).
• after replication the chromosomes arrange into pairs.
• the first division the chromosomes pairs line up in the centre of the cell
• the pairs pull apart so each new cell only has one copy of each chromosome (father’s and mother’s)
• in second division the chromosmes line up again in the centre of the cell. The arms are pulled aprt.
• you get four gametes, each with single set of chromosomes in it. Each gamete is gentically different as the chromosomes are all shuffled up.

Question 20

How does the cell produced by gamete fusion replicate itself

Answer 20

After two gametes fuse the resulting new cell divides by mitosis and repeates many times to form an embryo. The cells then diffrinciate and become specialised.

Question 21

Some characteristics are controlled by a single gene, such as:

Answer 21

fur colour in mice; and red-green colour blindness in humans. Each gene may have different forms called alleles.

Question 22

A dominant allele

Answer 22

A dominant allele is always expressed, even if only one copy is present.

Question 23

A recessive allele

Answer 23

A recessive allele is only expressed if two copies are present (therefore no dominant allele present).

Question 24

What do alleles presented/genotype do

Answer 24

The alleles present, or genotype, operate at a molecular level to develop characteristics that can be expressed as a phenotype.

Question 25

If the two alleles present are the same the organism is …

Answer 25

homozygous for that trait

Question 26

What is heterozygous

Answer 26

If its two alleles are for a particular gene are different

Question 27

What are Most characteristics are a result of

Answer 27

multiple genes interacting, rather than a single gene.

Question 28

What is your genotype

Answer 28

The combination of alleles you have (allele that is present in an individual).

Question 29

What is your phenotype

Answer 29

Characteristics you have to determine the genotype

Question 30

What is Polydactyly

Answer 30

(having extra fingers or toes) is caused by a dominant allele.

Question 31

What is cystic fibrosis

Answer 31

(a disorder of cell membranes) is caused by a recessive allele. It results in the body producing a lot of thick sticky mucus in the air passages and pancreas

Question 32

How does IVF detect inherited disorders such as cystic fibrosis

Answer 32

Embryos are fertilised in a lab and then implanted into mother’s womb. Beofre being implanted. It’s possible to remove a cell and analyse its genes. It is also possible to get DNA from the embryo in the womb.

Question 33

For embyonic screening

Answer 33

It will help people stop suffering.
Costs Government and taxpayers lots of money
Laws to stop it going to far (cannot select sex of baby).

Question 34

Against embryonic screening

Answer 34

Implies people are undesirable with genetic problems
It is expensive
Screening could lead to terminate pregnancy