Protein synthesis

Question 1

How is DNA stored in eukaryotes?

Answer 1

DNA in eukaryotes is linear, stored as chromosomes, and found in the nucleus. It is wound around proteins called histones and coils tightly to form chromosomes.

Question 2

How is DNA stored in prokaryotes?

Answer 2

DNA in prokaryotes is shorter, circular, not wound around histones, and condensed by supercoiling.

Question 3

What is a gene?

Answer 3

A gene is a sequence of DNA bases that codes for a polypeptide or functional RNA.

Question 4

What determines the primary structure of a protein?

Answer 4

The sequence of amino acids, which is determined by the sequence of bases in a gene, determines the primary structure of a protein.

Question 5

What is meant by “triplet” and “degenerate” in the genetic code?

Answer 5

Each amino acid is coded for by a sequence of 3 bases (triplet). The code is degenerate because more than one codon can code for the same amino acid.

Question 6

What is the function of mRNA?

Answer 6

mRNA is a transcript of a gene used to build a protein in translation.

Question 7

What is the function of tRNA?

Answer 7

tRNA carries amino acids to ribosomes during translation. It has a complementary anticodon to the codons on mRNA.

Question 8

What is rRNA and its role?

Answer 8

rRNA is the primary component of ribosomes and helps catalyse the synthesis of polypeptides.

Question 9

What are introns and exons?

Answer 9

Introns are non-coding sections of DNA that do not code for polypeptides. Exons are the coding sections of DNA.

Question 10

What are non-coding repeats?

Answer 10

Non-coding repeats are DNA sequences with multiple repeats that do not code for amino acids.

Question 11

What is an allele?

Answer 11

An allele is a slightly different version of a gene that codes for a slightly different version of a polypeptide.

Question 12

What happens in transcription?

Answer 12

1. DNA polymerase attaches to the beginning of a gene. 2. DNA helicase breaks H-bonds to unwind DNA. 3. One strand acts as a template to form mRNA. 4. Free RNA nucleotides pair with exposed bases, joined by RNA polymerase. 5. RNA polymerase stops at a stop signal. 6. mRNA leaves the nucleus.

Question 13

How does translation occur?

Answer 13

1. mRNA attaches to a ribosome. 2. tRNA brings amino acids and pairs its anticodon with the first codon on mRNA. 3. A second tRNA binds, and amino acids join by peptide bonds. 4. This continues until a stop codon is reached. 5. The polypeptide chain detaches.

Question 14

What is a mutation?

Answer 14

A mutation is a change in the sequence of DNA bases that affects coding for amino acids.

Question 15

What does it mean that DNA is “non-overlapping”?

Answer 15

Base triplets do not share bases; each base is part of only one triplet.

Question 16

Why is DNA described as “degenerate” and “universal”?

Answer 16

DNA is degenerate because multiple codons can code for the same amino acid. It is universal because the same triplets code for the same amino acids in all organisms.

Question 17

What is an insertion mutation?

Answer 17

An insertion is when a new base is added, causing a frame shift.

Question 18

What is a deletion mutation?

Answer 18

A deletion is when one or more bases are removed, causing a frame shift.

Question 19

What is a substitution mutation?

Answer 19

A substitution occurs when one base is replaced by a different base.

Question 20

What happens in inversion and duplication mutations?

Answer 20

Inversion: A group of bases is reversed. Duplication: One or more bases are repeated.

Question 21

What is nondisjunction, and what condition can it cause?

Answer 21

Nondisjunction occurs when chromosomes fail to separate during meiosis, leading to gametes with extra chromosomes. It can cause conditions like Down’s syndrome.

Question 22

What is the impact of frame shift mutations?

Answer 22

Frame shift mutations change the sequence of triplets, producing different amino acids and altering protein structure and function.

Question 23

How do mutations contribute to natural selection?

Answer 23

Mutations create genetic variation, increasing chances of survival through natural selection.

Question 24

What happens during Prophase I of meiosis?

Answer 24

The nuclear membrane breaks down, chromosomes condense, and crossing over may occur.

Question 25

What happens during Metaphase I of meiosis?

Answer 25

Chromosomes line up along the equator of the spindle.

Question 26

What happens during Anaphase I of meiosis?

Answer 26

Whole chromosomes are pulled to opposite poles of the spindle.

Question 27

What happens during Telophase I of meiosis?

Answer 27

Chromosomes reach the poles, the nuclear envelope reforms, and cytokinesis occurs.

Question 28

What happens during Prophase II of meiosis?

Answer 28

The nuclear membrane and nucleolus break down again.

Question 29

What happens during Metaphase II of meiosis?

Answer 29

Chromosomes line up separately along the equator of the spindle.

Question 30

What happens during Anaphase II of meiosis?

Answer 30

Centromeres divide, and chromatids are pulled apart to opposite poles.

Question 31

What happens during Telophase II of meiosis?

Answer 31

The nuclear membrane reforms, and cytokinesis produces 4 haploid daughter cells.

Question 32

How does genetic variation occur during meiosis?

Answer 32

Genetic variation occurs due to the different orientations of chromosomes in Metaphase I and Metaphase II.

Question 33

What are the key differences between mitosis and meiosis?

Answer 33

Mitosis produces 2 identical diploid cells for growth and repair, while meiosis produces 4 non-identical haploid cells for reproduction.

Question 34

What are the two types of variation?

Answer 34

Discontinuous variation: qualitative, distinct categories, controlled by one gene. Continuous variation: quantitative, controlled by many genes and influenced by environment.