Genetics And Reproduction Review

Question 1

Define chromosome

Answer 1

Chromosome -​packaged DNA. It is the DNA molecule surrounded by a protein sheath. There are 46 of them in human cells except gametes. They take a different form when the cell is dividing during mitosis or meiosis

Question 2

What is a nucleotide?

Answer 2

It is a three part unit consisting of a phosphate molecule, a sugar molecule and a nitrogen-containing base.

Question 3

What are the 4 nitrogen-containing bases

Answer 3

i) Adenine - A
ii) Thymine - T
iii) Cytosine - C
iiii) Guanine - G

Question 4

What is the base pairing rule?

Answer 4

adenine bonds with thymine (A with T)

cytosine bonds with guanine (C with G)

Question 5

5. If one side of a DNA molecule has the nitrogen-containing bases
   TAC CGC ATG, what is the base sequence on the other side (complementary side)?

Answer 5

ATG GCG TAC

Question 6

What is a gene?

Answer 6

A gene is the unit of heredity. It is a short section on the DNA molecule responsible for a particular trait or characteristic. It codes the instruction for a particular characteristic such as hair colour or blood type.

Question 7

What is a triplet code?

Answer 7

A triplet code consists of three nitrogen bases in sequence at the gene site. Each group of three bases represents a specific amino acid.

Question 8

How many individual chromosomes are in human cells? How many pairs of chromosomes are there in human cells?
What are these pairs called?

Answer 8

46
23
What are these pairs called? Homologous pairs. A homologous pair is two chromosomes with information about the same characteristic. One member of the pair is inherited from the mother, the other member of the pair is inherited from the father. The actual set of instructions (alleles) on each chromosome of the pair may be different but each chromosome of the pair is carrying genes concerning the same set of characteristics or traits. (Note: in the male the 23rd pair is not homologous)

Question 9

What is RNA?

Answer 9

Ribonucleic acid - It has a similar structure to DNA but it is a single strand that contains uracil instead of thymine as one of its four nitrogen-containing bases, and its sugar molecule is a ribose sugar.

Question 10

10. What is the full name of rRNA and what is its role?

Answer 10

The full name of rRNA is ribosomal RNA. It is formed in the nucleolus and its role is to link up with proteins made in the cytoplasm to form organelles called ribosomes.

Question 11

What is the full name of mRNA and what is its role?

Answer 11

The full name of mRNA is messenger RNA. It is a single stranded RNA molecule that copies the complete set of instructions at the gene site from one side of the DNA molecule, and carries these codons to the ribosome in the cytoplasm of the cell.

Question 12

What is the full name of tRNA and what is its role?

Answer 12

The full name of tRNA is transfer RNA. Each tRNA is a small molecule that contains one sequence of 3 nucleotides (a triplet), the anti-codon, from the other side of the DNA molecule in the nucleus and carries this information out of the nucleus and into the cytoplasm. In the cytoplasm it finds the amino acid that matches its anti-codon, and then brings this amino acid to the mRNA at the ribosomal site.

Question 13

Define DNA

Answer 13

DNA (Deoxyribonucleic acid) - two strands of nucleotides joined at their nitrogen bases forming a helix. It contains all the genetic material of an organism. This genetic information is the set of instructions for building proteins. It is found in the nucleus of the cell

Question 14

How do proteins differ from each other?

Answer 14

Proteins differ from one another in the type, number or sequence of amino acids in the protein chain.

Question 15

Give examples of different types of proteins in the body?

Answer 15

Enzymes, hormones, plasma proteins, antibodies, muscle fibre (actin and myosin) etc.

Question 16

What is the name given to the type of cell division most cells (somatic cells) of the body undergo?

Answer 16

Mitosis – A type of cell division that produces body cells (somatic cells) such as skin cells. Mitosis produces two new daughter cells that are identical to each other and the parent cell they originated from. Each new cell contains the same number of chromosomes as the parent and is referred to as a diploid cell. In the case of the human, the number of chromosomes in the diploid cell is 46 chromosomes, the diploid number.

Question 17

What is the name given to the type of cell division only sex cells (gametes) undergo?

Answer 17

Meiosis – A type of cell division which produces gametes (sex cells). Meiosis produces four new cells that are different from each other and from the germinal cell they originated from. Each new cell will contain only half the number of chromosomes (or a half set of chromosomes) as the parent cell. These are haploid cells and in the human these cells contain 23 chromosomes, a half set of chromosomes. Because of crossing over of genetic information during Prophase 1, the chromosomes are no longer identical to the parent cell. These new cells will mature to become eggs in the female and sperm in the male. (Note: only one egg will proceed through Meiosis II and it will only fully complete Meiosis II if fertilized.)

Question 18

Define interphase. What happens to the chromosomes during interphase?

Answer 18

Interphase is the phase in which a cell is working (e.g. cellular respiration, protein synthesis etc.). 90% of a cell’s life is spent in Interphase. The end of interphase is marked by the chromosomes replicating or duplicating themselves. In the human cell 46 chromosomes in the form of chromatin net duplicate, resulting in 92 chromosomes.

Question 19

Define cytokinesis. -

Answer 19

Cytokinesis – Is the division of the cytoplasm and organelles resulting in the production of two new daughter cells that are identical to the parent cell and to each other.

Question 20

Define the term diploid.

Answer 20

A cell having a full set of chromosomes. In the human that is 46 chromosomes in each cell. The diploid number is 46.

Question 21

Define the term haploid.

Answer 21

Having one half the number of chromosomes as a normal cell. Sperm and eggs are haploid cells having only 23 chromosomes, half the number as the original germinal cell. The haploid number is 23

Question 22

Name two significant phases during Meiosis that will ensure genetic diversity?

Answer 22

i) Prophase 1 – the crossing over of information from one non-sister chromatid to another in the tetrad (bundle of four).
ii) Anaphase 1 – when the homologous pairs of sister chromatids separate from each other. Setting up for the final four cells that will each contain only one chromatid from the homologous pairs of sister chromatids (only one member of the bundle of four)