Topic 3- Genetics

Question 1

What is DNA?

Answer 1

DNA is a chemical that carries genetic information and is found in the chromosomes, which are found in the nucleus of most cells.

Question 2

What does DNA stand for?

Answer 2

Deoxyribose Nucleic Acid.

Question 3

What are the 4 complementary base pairs?:

Answer 3

The complementary base pairs join the strands in a double helix of DNA together they are

• adenine
• thymine
• cytosine
• guanine

Question 4

What base pairs in DNA go together and why?

Answer 4

A-T go together and C-G go together.
This is because between the base pairs there are hydrogen bonds.
Parts of the DNA bases are slightly charged. A slightly negative charged base attracts a slightly positive charged base. THIS FORMS A WEAK HYDROGEN BOND.

Question 5

What is the shape of DNA?

Answer 5

A molecule of DNA contains 2 strands that form a helix. The two strands are joined together by the complementary base pairs to form a double helix.

Question 6

What is a genome?

Answer 6

The genome is the entire length of your DNA.
(The nuclei of your cells contain very long molecules of dna each molecule is tightly folded and cooled to make a chromosome.)

Question 7

What is the DNA code?

Answer 7

The order of bases in a gene contain the coded instructions for a protein. We have different genes because of the slight differences I the order of our bases.

Everyone has different DNA except identical twins.

Question 8

What does RNA stand for?

Answer 8

Ribonuclease acid

Question 9

In protein synthesis what are the bases and what are the bases

Answer 9

• adenine
• cytosine
• guanine
• uracil

U replaces T so the base pairs are:
C-G
A-U

Question 10

Explain the basic steps of transcription in protein synthesis?

Answer 10

1) an enzyme called RNA polymerase attaches to the DNA.
2) It attaches to the DNA in front of a non coding region (called non coding region because it contain ps no code for a protein)
3) The enzyme separates the 2 DNA strands .
4) The enzyme moves along the DNA strand (the template strand) adding complementary nucleotides.
5) The nucleotides link to form a strand of messenger RNA (mRNA).

Question 11

Describe the basic steps of translation in protein synthesis?

Answer 11

1) The mRNA strand travel out the nucleus through nucleur pores.
2) In the cytoplasm The mRNA strands attach to ribosomes.
3) a ribosome moves along a mRNA stand 3 bases at a time. EACH TRIPLET OF BASES IS CALLED A CODON.
4) At each mRNA codon a molecule of transfer RNA (tRNA) with bases line up.
5) Each tRNA molecule carries a specific amino acid.
6) As the ribosome moves along it joins the amino acids from tRNA molecules together to form a polypeptide chain.

Question 12

What are Mendel’s 3 laws of inheritance?

Answer 12

• Each gamete receives only one factor for characteristics.
• The version of a factor that a gamete receives is random and does not depend on the other factors in a gamete.
• Some versions of a factor are more powerful than others and always have an effect of the offspring.

Question 13

What is an allele?

Answer 13

Different forms of the same genes are called alleles

Question 14

What does homozygous mean?

Answer 14

If both alleles for 1 gene are the same an organism is homozygous for that gene. This is the more dominant.

Question 15

What does heterozygous mean?

Answer 15

If alleles are different for one gene. This is the less dominant genotype.

Question 16

Describe what phenotype and genotypes are?

Answer 16

Genotype: The allele of an organism.(Its gene)

Phenotype: What an organism looks like.

Question 17

When are recessive characteristics seen?

Answer 17

A recessive characteristic is only seen if both alleles are recessive.

Question 18

In punnet squares what letters represent male female ?

Answer 18

The egg cell contains X chromosomes and the sperm contains X&Y chromosomes.

IT IS THE SPERM CELL THAT DETERMINES THE SEX OF THE OFFSPRING.

Question 19

What is the ABO blood group?

Answer 19

Everyone’s blood is one of four blood groups. A, B, AB, O. Which blood group you have is determined by weather you have a certain ‘marker molecule’ on the outside of your red blood cells.

The marker molecules are A, B, O.

Question 20

What does co-dominant mean and give an example?

Answer 20

Co-dominance occurs when both the alleles for a gene affect the phenotype.
A B
A person with a (blood) genotype I and I Shoe the affects of both blood groups AB.

Question 21

What is melanin?

Answer 21

The OCA2 gene controls the amount of melanin produced. Melanin is a protein that controls the colour of hair skin and eye colour and the darkness of it.

The more melanin someone has the darker their hair skin and eye colour.

Question 22

When do mutations occur?

Answer 22

Mutations can be caused by:

• a change in the bases of genes
• When DNA is not copied properly in cell division
• environmental factors.

THIS IS MORE LIKELY TO HAPPEN IF THERE IS DAMAGE TO THE DNA BY RADIATION CERTAIN SUBSTANCES.

Question 23

What are the 3 possible phenotypic outcomes from a genetic mutation?

Answer 23

• A genetic mutation results in no change to the phenotype.
• a genetic mutation could result in a small change to the phenotype.
• a genetic mutation can rarely, lead to a large change in the phenotype.

Question 24

How is genetic variation caused?

Answer 24

This is caused by different alleles inherited during sexual reproduction.

Question 25

What are polypeptides and how are they made?

Answer 25

As the ribosomes move along the DNA it joins the amino acids from the tRNA molecules together forming a polypeptide.

A POLYPEPTIDE IS A CHAIN OF AMINO ACIDS.

Question 26

Sex linkage disorders:

Answer 26

Chromosomes in diploid cell comes in pairs. Most chromosomes have the same genes however the male human Y sex chromosome is shorter that the X and therefore is missing some of the genes found on X. This means a man may only have one allele for some genes of the X chromosome and if there is a genetic disorder he will inherit it.