DNA and inheritance

Question 1

Where is DNA found?

Answer 1

The nucleus of a cell.

Question 2

What are the 6 key points regarding DNA?

Answer 2

• DNA forms a chemical code which acts as instructions for the cell to make proteins.
• The make-up of the DNA molecule varies in different individuals, although it is made up of the same basic components.
• All living processes are a series of chemical reactions in cells.
• All these reactions are are controlled by enzymes.
• All enzymes are proteins.
• The chemical reactions that a cell can carry out are therefore determined by the makeup of the DNA in that individual.

Question 3

What is DNA made up of?

Answer 3

DNA is made up of 2 long chains of alternating sugar and phosphate molecules connected by pairs of bases.

Question 4

What is the shape of DNA?

Answer 4

The ladder like structure are twisted to form a double helix shape.

Question 5

What are the 4 bases of DNA?

Answer 5

Adenine (A) and thymine (T), guanine (G) and cytosine (C).

Question 6

What do bases do?

Answer 6

Bases form the instructions, in a code, for the manufacture of proteins. It determines which amino acids are used to make a given protein and in what order.

Question 7

What is the ‘code’?

Answer 7

The ‘code’ consists of triplets of bases along the DNA. Each triplet codes for an individual amino acid in the protein.

Question 8

What is in the nucleus of a cell?

Answer 8

The long DNA molecules are coiled up into structures called chromosomes. DNA is the raw material of genes - a gene is a short length of DNA that codes for 1 protein.

Question 9

What is genetic profiling?

Answer 9

You can look at the bases in a DNA molecule and see to what extent different DNA samples are similar. This analysis produces a genetic profile. The genetic profiling process can be used to show the similiarity between 2 different samples.

Question 10

What are the uses of genetic profiling?

Answer 10

• Criminals can be positively identified if DNA samples from the crime scene match theirs.
• If there is a dispute as to who is the father of a child, the father DNA will have many similarities to the child’s.
• The DNA of a species can be compared with each other to establish how closely related they are. The more closely related, the more similar the DNA.
• Genetic profiling can detect certain genes that may be associated with a particular disease. This opens up the possibilities of treatment.

Question 11

What are the steps of carrying out genetic profiling?

Answer 11

1 - a sample of the cells is collected (e.g blood or skin). These cells are broken up and the DNA extracted.
2 - the DNA is ‘cut up’ by enzymes so that it ends up in fragments of different sizes.
3 - the fragments are then separated, a pattern develops, which is the genetic profile.

Question 12

What is a gene?

Answer 12

A length of DNA that codes for one protein.

Question 13

What is an allele?

Answer 13

A variety of a gene.

Question 14

What is a chromosome?

Answer 14

A length of DNA that contains many genes, found in the nucleus and is visible in cell division.

Question 15

What is a genotype?

Answer 15

The genetic make-up of an individual (cc, CC, Cc).

Question 16

What is phenotype?

Answer 16

The description of the way the genotype shows itself (blue eyes, brown hair, short/tall).

Question 17

What is meant by dominant?

Answer 17

An allele that shows in the phenotype whenever it is present (shown by an uppercase letter).

Question 18

What is meant by recessive?

Answer 18

An allele that is hidden when when a dominant allele is present (shown by a lower case letter).

Question 19

What is meant by F1/F2?

Answer 19

Short for first generation and second generation in a genetic cross (in plants).

Question 20

What is homozygous/homozygote?

Answer 20

A homozygote contains 2 identical alleles for the gene concerned - it is homozygous.

Question 21

What is heterozygous/heterozygote?

Answer 21

A heterozygote contains 2 different alleles for the gene concerned - it is heterozygous.

Question 22

What is ‘selfing’?

Answer 22

A technique by which pollen from a plant is used to fertilise ovules in the flowers of the same plant.

Question 23

What are the 4 basic rules of inheritance?

Answer 23

• There are copies of each gene in the body, one coming from each parent.
• The gametes contain one copy of each gene.
• The copies are not necessarily the same, as every gene has different versions called alleles.
• Individuals may have 2 of the same alleles for a particular gene (homozygous) or 2 different alleles (heterzygous).

Question 24

What is monohybrid inheritance?

Answer 24

Monohybrid inheritance is the name given to the inheritance of one gene.

Question 25

What would Aa x Aa give you?

Answer 25

3:1 ratio of dominant:recessive phenotypes.

Question 26

What would Aa x aa give you?

Answer 26

1:1 ratio of dominant:recessive phenotypes.

Question 27

What is ‘genetic modification’?

Answer 27

Extracting genes from one organism and putting them into another and can also swap one gene for another. It is often done is food (GMOs).

Question 28

Advantages to genetic modification?

Answer 28

• Crops can be designed to survive difficult farming conditions found in many of the worlds poorer countries (e.gin very hot or dry countries).
• Crops can have a gene inserted that makes them resistant to herbicides. Using the herbicide will then only kill weeds and this could greatly increase the yield of food crops.
• Plants can be modified to produce oils and other substances that can be used as biofuels, saving non renewable resources.

Question 29

Disadvantages to genetic modifications?

Answer 29

• Sometimes the inserted genes has side effects (e.g genetically modified soya plants had stems that would spilt in hot conditions).
• Pollen from genetically modified crops can easily get carried out of the farm by wind or insects and this could introduce the gene into the natural population.
• GM plants could become established outside the farm and if they are herbicide resistant, could be become a pest.

Question 30

Ethical issues of genetic modifications?

Answer 30

• The technology is expensive and only richer countries can afford it. If they develop new supercrops then poorer countries won’t be able to compete.
• The large companies which develop GM crops can patent a crop so that only they can produce it. In theory, they then could change what they like as there will be no competition.