BIO Set #3 Possible Short Essay Questions Exam

Question 1

Nitrogenous base pairings and Chargaff’s Rule

Answer 1

This rule helps to explain why A always pairs with T, and G always pairs with C. It also helps us understand how DNA can be replicated accurately.

The amount of Adenine (A) is equal to the amount of Thymine (T).
The amount of Guanine (G) is equal to the amount of Cytosine (C).

Question 2

Differences and similarities between RNA and DNA

Answer 2

SIMILARITES
Both DNA and RNA are nucleic acids made up of nucleotides,which
- consist of a sugar,
- a phosphate group
- and a nitrogenous base.

DIFFERENCES
- DNA is double-stranded
- RNA is single-stranded
- DNA contains the base thymine (T)
- RNA contains Uracil (U)
- DNA sugar is deoxyriose
- RNA sugar is ribose

Question 3

Explain what is Strand separation and what enzymes are involved?

Answer 3

Strand separation refers to the process of separating the two strands of a DNA double helix, essentially “unzipping” it, which is primarily carried out by an enzyme called DNA helicase; this step is crucial for DNA replication as it allows each strand to serve as a template for the synthesis of a new complementary strand

Key points about strand separation:
Enzyme involved:
DNA helicase actively breaks the hydrogen bonds between base pairs on the DNA strands, allowing them to separate and unwind.

Replication fork:
The area where the DNA strands are separated creates a Y-shaped structure called the replication fork.

Role of other proteins:
While helicase is the primary enzyme responsible for strand separation, other proteins like single-strand binding proteins stabilize the separated strands to prevent them from re-annealing before replication occurs.

Question 4

Proofreading and DNA repair

Answer 4

DNA proofreading and repair are mechanisms that cells use to prevent mutations, or permanent changes in DNA sequence

Question 5

The phases of protein synthesis

Answer 5

Protein synthesis is the process in which cells make proteins. It occurs in two stages: transcription and translation. Transcription is the transfer of genetic instructions in DNA to mRNA in the nucleus

Question 6

Differences between mitosis with meiosis I and II.

Answer 6

mitosis produces two genetically identical diploid daughter cells from one parent cell.

while meiosis produces four genetically diverse haploid daughter cells through two rounds of division, with

meiosis I being the reduction division where homologous chromosomes separate, and

meiosis II where sister chromatids separate, effectively halving the chromosome number in the daughter cells compared to the parent cell.

Question 7

Prophase I and metaphase I of meiosis

Answer 7

a cell division process that occurs in germ cells to produce gametes

Prophase I
Chromosomes condense, the nuclear membrane breaks down, and homologous chromosomes pair up to form tetrads. During this stage, homologous chromosomes exchange genetic material through a process called crossing over, which creates genetic variation.
Metaphase I
Tetrads line up in the middle of the cell along the metaphase plate. Microtubules from the centrosomes at opposite poles of the cell attach to the kinetochores of each chromosome. The arrangement of the pairs of chromosomes is random, a process called independent assortment.

Meiosis I is one of two divisions required to produce gametes, with the other being meiosis II. Meiosis II is similar to a mitotic division.

Question 8

Variation

Two parents

Answer 8

“Variation in meiosis” refers to the generation of genetic diversity within daughter cells produced during meiosis, primarily occurring through two key mechanisms: crossing over (recombination) between homologous chromosomes and independent assortment of chromosomes during metaphase I, resulting in unique combinations of alleles in each gamete produced.

Key points about variation in meiosis:
Crossing over:
When homologous chromosomes pair up during prophase I, they exchange genetic material at specific points called chiasmata, leading to new chromosome combinations with mixed alleles from both parents.

Independent assortment:
During metaphase I, the maternal and paternal chromosomes line up randomly at the equator of the cell, allowing for independent segregation of alleles to different daughter cells.

Resulting diversity:
Due to these mechanisms, each gamete produced during meiosis carries a unique combination of alleles, contributing significantly to genetic variation within a species.

Question 9

Oogenesis and Spermatogenesis

Answer 9

Oogenesis and spermatogenesis are the processes that create female and male gametes, or sex cells, respectively:

Oogenesis
The process of creating ova, or egg cells, in the ovaries. The resulting gamete contains a haploid nucleus, as well as organelles, cytoplasmic enzymes, metabolic substrates, and mRNAs.

Spermatogenesis
The process of creating sperm cells in the testes. The resulting gamete is essentially a motile nucleus.