Inheritance - DNA

Question 1

Where is DNA found

Answer 1

in the chromosomes

Question 2

what is DNA

Answer 2

a polymer made up of two strands forming a double helix

Question 3

why is DNA our genetic material

Answer 3

because our DNA determines our inherited features

Question 4

what is a gene

Answer 4

a small section of DNA on a chromosome

Question 5

how are proteins made

Answer 5

by joining together amino acids

Question 6

what do genes do

Answer 6

each gene codes for a specific sequence of amino acids to make a specific protein

Question 7

what is the genome

Answer 7

the entire genetic material of an organism

Question 8

what are the benefits of the human genome

Answer 8

• understanding the human genome will help us search for genes that are linked to a specific disease, e.g - genes that are linked to cancer or Alzheimer’s
• Understanding the human genome may help us understand and treat inherited disorders such as Cystic fibrosis
• We can use the human genome to trace human migration patterns from the past, and this can help people discover their ancestry

Question 9

what are DNA strands made from

Answer 9

nucleotides

Question 10

what are nucleotides made up of

Answer 10

• a sugar
• a phosphate
• a base

Question 11

what does the circle represent in a nucleotide

Answer 11

the phosphate group

Question 12

what does the pentagon represent in a nucleotide

Answer 12

the sugar

Question 13

what does the rectangle represent in a nucleotide

Answer 13

the base

Question 14

what does complementary mean in terms of DNA bases

Answer 14

the same bases always pair on opposite strands

Question 15

which bases pair to which in DNA

Answer 15

A and T pair
C and G pair

Question 16

how many different amino acids are there in humans

Answer 16

20

Question 17

what is the order of amino acids in a protein determined by

Answer 17

the sequence of bases in the gene for that protein

Question 18

Stages of protein synthesis

Answer 18

1. Proteins are made in the cell cytoplasm on tiny structures called ribosomes
2. To make proteins, ribosomes use the code in the DNA, and dna is found in the nucleus, and cant move our as its too big, so the cell needs to get the code from the DNA to the ribosomes
3. This is done using a molecule called mRNA which is made by copying the code from the DNA. The mRNA acts as a messenger between the DNA and ribosomes- carrying the code between the two
4. the correct amino acids are brought to the ribosomes in the correct order by carrier molecules

Question 19

what are proteins

Answer 19

polymers of amino acids

Question 20

what does the order of amino acids in a protein determine

Answer 20

its shape and function

Question 21

what is mRNA

Answer 21

a single stranded molecule

Question 22

what is a mutation

Answer 22

a change to a base of DNA

Question 23

why might mutations not change an amino acid sequence

Answer 23

because different base triplets can sometimes encode for the same amino acid

Question 24

why might a mutation which changes the shape of a protein, have a massive effect on it

Answer 24

• because the active site of the enzyme may change shape, so it’ll no longer attach to the substrate
• if the mutation changes the shape of a structural protein such as collagen, it may lose it’s strength

Question 25

what do non coding parts of DNA do

Answer 25

they switch genes on and off, they tell genes when to produce proteins

Question 26

what would happen if a non - coding part of DBA was mutated

Answer 26

a gene may be turned off when it’s meant to be turned on, or vice versa - meaning a cell would produce a protein that its not meant to have at the time - this could have a very significant effect on the cell, eg uncontrolled mitosis leading to cancer

Question 27

what are alleles

Answer 27

versions of genes

Question 28

what is a genotype

Answer 28

something that tells us what alleles are present in a person

Question 29

meaning of homozygous alleles

Answer 29

having two copies of the same allele

Question 30

what is a phenotype

Answer 30

something that tells us the characteristics caused by the persons alleles

Question 31

what is heterozygous

Answer 31

when someone has two different alleles

Question 32

what is a dominant allele

Answer 32

an allele that will show in the phenotype even if there is only one copy present

Question 33

what is a recessive allele

Answer 33

an allele that will only show in the phenotype if two copies are present( so if no dominant alleles are present)

Question 34

what is cystic fibrosis

Answer 34

a disorder of the cell membranes

Question 35

what needs to happen in order for a person to have cystic fibrosis

Answer 35

they need to have two copies of the defective allele

Question 36

what is meant by a carrier of cystic fibrosis

Answer 36

when a person has one defective allele and one normal allele

Question 37

What is polydactyly

Answer 37

a disorder where someone is born with extra fingers or toes

Question 38

what type of allele is polydactyly caused by

Answer 38

dominant

Question 39

what is embryo screening

Answer 39

a process in which embryos are tested to see if they have the alleles for inherited disorders

Question 40

how does embryo screening work

Answer 40

1. cell is taken out of and embryo is tested to see if it has the alleles for an inherited disorder 2. Embryo which do not have the defective alleles are implanted into the woman 3. These can help them develop healthy offspring

Question 41

what are issues around embryo screening

Answer 41

- its expensive, and people think that the money should be spent elsewhere un the health service - implies that people with genetic problems are undesirable and this may cause prejudice - in the future we may be able to screen embryos to produce offspring with desirable features, this is also unethical - often, a large number of embryos are created, but only a small number are implanted, meaning that some healthy embryo are destroyed and people think its unethical

Question 42

what is gene therapy

Answer 42

- correcting faulty alleles and using these to treat inherited disorders

Question 43

what chromosomes do males have

Answer 43

XY

Question 44

what chromosomes do females have

Answer 44

XX

Question 45

where does the first stage of protein synthesis happen

Answer 45

nucleus

Question 46

where does the second stage of protein synthesis take place

Answer 46

cytoplasm

Question 47

Summarise the stages of protein synthesis

Answer 47

1. Transcription - the base sequence of the gene is copied into a complementary template molecule - scientists call this template mRNA and it is a single stranded molecule 2. the mRNA then passes out of the nucleus into the cytoplasm 3. Translation - In this stage, the mRNA molecule attaches to a ribosome. amino acids are then brought to the ribosome on carrier molecules - these carrier molecules are called tRNA 4. the ribosome then reads the triplets of bases on the mRNA and uses this to join the correct amino acids in the correct order 5. once the protein chain is complete, it now folds into its unique shape

Question 48

what happens when a protein formed

Answer 48

it folds into a unique shape

Question 49

What has to happen in order for someone to inherit cystic fibrosis

Answer 49

The person has to have two copies of the defective allele

Question 50

Why aren’t punnet squares that accurate?

Answer 50

Because they are just probabilities

Question 51

how do DNA bases in a gene code for specific chains of amino acids

Answer 51

- each sequence of the three bases codes for one specific amino acids, so the order of the bases in the gene decides the order of amino acids in the chain

Question 52

advantages of embryo screening

Answer 52

- will help people stop suffering from genetic disorders - treating these disorders. it’s the government and taxpayers a lot of money, screening to reduce the number of people suffering from these disorders could save money - parents can’t use it to select desirable characteristics as there are laws to stop screening going to far