Topic 3: DNA, enzymes, meiosis, monohybrid genetics, mutations, HGP.

Question 1

What shape is DNA

Answer 1

A double helix.

Question 2

What are the four bases?

Answer 2

a,t and c,g (these always go together like that)
adenine
cytosine
guanine
thymine.

Question 3

What is a nucleotide?

Answer 3

A grouping in which a base is attached to a sugar and each sugar is attached to a phosphate group.

Question 4

What is a mutation?

Answer 4

A gene mutation is a change in the order of bases on a strand of DNA which affect anything that that dna section codes for.

Question 5

What is substitution?

Answer 5

It is a mutation in which a base in the DNA sequence is changed, affecting the codon. with a differentDNA codon the mRNA changes as the complementary bases are different. this mean the translation process changes making the tRNA anti codon different to what it should be. With different tRNA, the amino acid is different to what it should therefore changes the shape of the protein.

Question 6

What are enzymes?

Answer 6

Proteins that act as a biological catalyst in order to bring about a specific reaction. e.g. to brake down food.

Question 7

How do enzymes brake down substrates?

Answer 7

The enzyme specific active site collides with the complementary substrate. Activation energy starts the reaction in which the substrate gets broken down into two separate products.

Question 8

What is activation energy?

Answer 8

The energy required for a reaction to take place.

Question 9

What does denatured mean in enzymatic terms?

Answer 9

When the active site changes shape so it is no longer complementary to the substrate due to extreme temperature or Ph.

Question 10

What is amylase?

Answer 10

An enzyme catalyses the reaction from starch into sugars.

Question 11

What does Lipase do?

Answer 11

catalyses the reaction of lipids into fatty acids and glycerol

Question 12

What do protease do?

Answer 12

catalyses he reaction of proteins into amino acids.

Question 13

What is meiosis?

Answer 13

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell and is used to create gametes. for example, a sperm cell has half the number of chromosomes as a normal body cell.

Question 14

How does meiosis happen?

remember the e otherwise it wont count because mitosis has a similar spelling

Answer 14

1) each chromosome is copied
2) move to the edges of the cell
3) The pairs of chromosomes divide into two separate cells
4) These cells divide again into two more cells with half the number of chromosomes. so these cells or gametes only have one copy of each chromosome

Question 15

What is an allele?

Answer 15

A variant of a gene from your parents.

Question 16

What does heterozygous mean?

Answer 16

when the offspring has two different alleles usually one dominant and one recessive. e.g c,C

Question 17

What does homozygous mean?

Answer 17

When the offspring has two of the same alleles. E.g C,C

Question 18

What is a genotype?

Answer 18

A genome is an organism’s complete set of DNA, including all of its genes. Each genome contains all of the information needed to build and maintain that organism.
If a question asks to state the genotype, it is asking for heterozygous or homozygous

Question 19

What is a phenotype?

Answer 19

What the effect of the allele is. e.g eye colour or if you have a genetic disease or not.

Question 20

What is a zygote?

Answer 20

A fertilised egg.

Question 21

What does it mean by a recessive allele?

Answer 21

An allele that doesn’t show any impact unless paired with another of the same recessive allele (c,c). e.g you need to of the alleles coding for blue eyes to have blue eyes.

Question 22

What does it mean by a dominant allele?

Answer 22

An allele that takes control/the one that is seen when the genotype is anything apart from two recessive alleles. It takes dominance over the recessive alleles.

Question 23

How to work out the probability of having a particular genotype.

Answer 23

Use a table/ grid(similar to that used in maths for multiplication) with the genotype of one parent at the top and the other at the side. remember dominant (capital) alleles take dominance.

Question 24

What is co-dominance?

Answer 24

This is when there are two DIFFERENT dominant alleles and they both take dominance creating a new genotype. most common in blood groups.

Question 25

What is cystic fibrosis?

Answer 25

A genetic disease and mutation that cause a build up of mucus in many organs and other small passages.

Question 26

What causes cystic fibrosis?

Answer 26

When both copies of the CFTR gene are faulty and don't work the way they are supposed too. Therefore they don't make the right protein which makes salt and prevents the cf. If only one of the cftr genes is faulty they will still make sufficient amounts of salt and therefore they are only a CARRIER of cystic f.

Question 27

What is genetic modification?

Answer 27

Certain enzymes can cut pieces of DNA with a desired characteristic from one organism, and join them into a gap in the DNA of another organism. This means that the new organism with the inserted genes has the genetic information for one or more new characteristics. For example, humans produce insulin and bacteria are genetically modified to carry that gene and produce insulin.

Question 28

What is the process of genetic modification? / how do they do it.

Answer 28

1) choose desired gene from the DNA 2) isolate that gene (cut it out) using a restriction enzyme, to leave a pair of sticky ends 3) The vector (e.g. bacteria for insulin) is cut using the same restriction enzyme also leaving sticky ends 4) .The vector and the isolated gene are joined together by ligase enzyme and inserted back into the vector 5) The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics.

Question 29

What are the letters of the bases that form the DNA code?

Answer 29

A, T | G, C

Question 30

What is transcription?

Answer 30

The first part of the processes of making proteins

Question 31

What are the steps of protein synthesis?

Answer 31

1) DNA unwinds and mRNA nucleotides attach to their complementary bases, replacing the other strand of DNA 2) mRNA being a single strand can fit through the nuclear pores and goes into the cytoplasm 3) tRNA anti-coden fits together with their complementary mRNA coden with its amino acid attached to the tRNA 4) The tRNA leaves it amino acid and as this process repeats, the amino acids build up into a chain called a protein.

Question 32

What is a substrate?

Answer 32

The stuff which gets broken down by an enzyme.

Question 33

What is an allele?

Answer 33

Alleles are different forms of a gene. They can be dominant or recessive

Question 34

What is a zygote?

Answer 34

a fertilised egg

Question 35

what is cystic fibrosis?

Answer 35

a genetic disease caused by both copies of the CFTR gene in chromosome 7 to be faulty. This is because of a mutation causing the wrong protein to made not the correct salt transportation protein. If you suffer from cystic fibrosis you will have build up of mucus in many organs like the lungs.

Question 36

What are sticky ends?

Answer 36

A short section of unpaired bases in the DNA usually cut by a restriction enzyme.

Question 37

How do you calculate the rate of reaction

Answer 37

amount of reactant used OR product formed/time

Question 38

How do you calculate rate of enzyme activity?

Answer 38

1/time

Question 39

What is polymerase?

Answer 39

a substance which aids the RNA nucleotides binding to the complementary DNA

Question 40

what are the advantages of asexual and sexual reproduction?

Answer 40

Asexual reproduction: quick and doesn't require a mate/fertilisation Sexual reproduction: allows for variation between offspring, reducing the chances of genetic disease and increased chances of survival

Question 41

What is the question asking for if it says 'state the genotype'?

Answer 41

homozygous or herozygous

Question 42

What is a plasmid?

Answer 42

A loop of extra DNA in a bacterial cell.

Question 43

Explain the iodine test

Answer 43

A few drops of iodine solution put into a solution to test for starch Colour of negative result: Yellow/orange Colour of positive result: blue/black

Question 44

Explain the benedict's solution test

Answer 44

Add benedict's solution to the solution and heat at 95'c to test for reducing sugars Colour of negative result: Blue Colour of positive result: Green -> orange -> red (depending on how much sugar present)

Question 45

Explain the biuret test

Answer 45

Contains potassium hydroxide solution and copper sulfate solution. Add this to the solution to test for protein. Colour of positive result: pale blue Colour of negative result: pale purple

Question 46

Explain the ethanol test

Answer 46

Add ethanol to a food solution to test for fat. Colour of negative result: clear Colour of positive result: cloudy