Term 2 Genetics

Question 1

What role does DNA plays in inheritance

Answer 1

DNA carries genetic information - the genetic code. The basis for this lies in the fact that DNA makes genes and genes make chromosomes.

Question 2

Describe the relationship between DNA, genes, chromosomes

Answer 2

Chromosomes carry DNA in cells. DNA is responsible for building and maintaining your human structure. Genes are segments of your DNA, which give you physical characteristics that make you unique.

Question 3

Describe how both genetic and environmental factors determine phenotypes

Answer 3

Environmental factors such as diet, temperature, oxygen levels, humidity, light cycles, and the presence of mutagens can all impact which of an animal’s genes are expressed, which ultimately affects the animal’s phenotype.

Question 4

What is a karyotype

Answer 4

A karyotype is an individual’s complete set of chromosomes. The term also refers to a laboratory-produced image of a person’s chromosomes isolated from an individual cell and arranged in numerical order.

Question 5

Recall the sex chromosomes for humans, and describe how these determine gender

Answer 5

Sex chromosomes in humans consist of two types: X and Y chromosomes. Females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

Question 6

Explain how the structure of DNA relates to its function

Answer 6

DNA’s double helix structure, with complementary base pairing (A-T, C-G), ensures stability, accurate replication, and accessibility for protein synthesis. Its sequence encodes genetic information, dictating traits and cellular functions.

Question 6

Describe the structure of DNA

Answer 6

Double helix formed by two antiparallel strands of nucleotides.
Each nucleotide consists of a phosphate group, a deoxyribose sugar, and one of four nitrogenous bases: adenine, thymine, cytosine, or guanine.

Question 7

What is Chargaff’s rule

Answer 7

Chargaff’s Rule states that adenine(A) pairs with thymine (T), and cytosine (C) pairs with guanine (G), ensuring complementary base pairing.

Question 8

Describe the relationship between DNA, genes and proteins

Answer 8

Genes are a region of DNA that act as instructions to create molecules called proteins.

Question 9

Describe the process of gene synthesis in regard to translation

Answer 9

Translation:
Occurs in the cytoplasm
mRNA is translated into a protein with the help of ribosomes and transfer RNA (tRNA)
tRNA delivers amino acids to the ribosome according to the mRNA codons
Ribosomes catalyze the formation of peptide bonds between amino acids to form a polypeptide chain

Question 9

Compare DNA and RNA

Answer 9

DNA:
Double-stranded
Sugar is deoxyribose
Bases include adenine (A), thymine (T), cytosine (C), and guanine (G)
Stable structure, less prone to degradation
Stores genetic information

RNA:
Single-stranded
Sugar is ribose
Bases include adenine (A), uracil (U), cytosine (C), and guanine (G)
Less stable, more prone to degradation
Involved in various cellular processes such as protein synthesis, gene regulation, and cell signaling

Question 9

Describe the process of gene synthesis in regard to transcription

Answer 9

Gene synthesis involves two main processes:

Transcription:
Occurs in the nucleus
DNA is transcribed into mRNA by RNA polymerase
mRNA carries the genetic code from the DNA to the ribosome

Question 10

Describe the process of mitosis

Answer 10

Type of cell division in somatic cells
Produces two identical daughter cells

One round of division (PMAT):
Prophase – the cell (P)repares for division: the chromosomes condense and the nucleus starts to break down
Metaphase – the chromosomes line up along the (M)iddle of the cell
Anaphase – the chromosomes separate and are dragged (A)way from each other
Telophase – (T)wo nuclei form, each with its own set of identical DNA

Results in diploid daughter cells (2n)
Occurs in growth, repair, and asexual reproduction

Question 11

Describe the process of Meiosis

Answer 11

Type of cell division in germ cells
Produces four non-identical daughter cells
Two rounds of division (PMAT I and PMAT II)
Results in haploid daughter cells (n)
Occurs in the formation of gametes (sperm and egg) for sexual reproduction

Question 12

Describe a Gene

Answer 12

Genes are made up of sequences of DNA and are arranged, one after another, at specific locations on chromosomes in the nucleus of cells that contain instructions for specific traits.
They determine the expression of a particular characteristic.
Genes can have multiple alleles.
They are located on chromosomes within the cell nucleus.
Mutations in genes can lead to variations in traits.

Question 13

Describe an Allele

Answer 13

Alleles are different forms of a gene.
They occupy the same position (locus) on homologous chromosomes.
Alleles can be dominant or recessive.
Individuals inherit one allele from each parent, resulting in a genotype.

Question 14

What was Mendel’s contributions to the study of genetics

Answer 14

Gregor Mendel is often referred to as the “Father of Genetics” for his groundbreaking work on the inheritance of traits.
He conducted experiments on pea plants in the mid-19th century and formulated the fundamental principles of inheritance, which laid the foundation for modern genetics.

Question 15

Why did Gregor Mendel choose pea plants

Answer 15

Variability: Pea plants exhibit a wide range of easily observable traits, such as flower color, seed shape, and plant height.

Controlled Breeding: Pea plants can self-fertilize or cross-fertilize, depending on the experimental design. Mendel could control the breeding process by manually pollinating specific plants, ensuring accurate records of parentage and offspring.

Short Generation Time: Pea plants have a relatively short life cycle, allowing for multiple generations to be studied within a reasonable timeframe.

Large Number of Offspring: Pea plants produce a large number of seeds per pod, providing ample material for statistical analysis

Ease of Cultivation: Pea plants are easy to cultivate and maintain in a controlled environment, making them ideal for experimental purposes.

Question 16

Describe some examples of human genetic traits

Answer 16

Eye colour, hair colour / texture, blood type, freckles, height, fingerprint

Question 17

Explain how mutations can occur

Answer 17

Spontaneous Mutations: Arise naturally during DNA replication, repair, or recombination due to errors by DNA polymerases or chemical changes in DNA bases.

Environmental Factors: Exposure to radiation, chemicals (mutagens), or biological agents can damage DNA, leading to mutations.

Mutagenic Chemicals: Directly interact with DNA, causing changes in its structure. Examples include alkylating agents and intercalating agents.

Transposons: DNA sequences that can move within the genome, disrupting genes or regulatory sequences when they insert into new locations.

DNA Replication Errors: Mistakes during DNA replication, such as incorrect nucleotide insertion, deletion, or skipping, can lead to mutations.

Errors in DNA Repair: Mistakes in DNA repair mechanisms can result in mutations if damage is not properly repaired or if repair enzymes introduce errors.

Question 18

Describe three different types of mutation

Answer 18

Point Mutation:

Involves changes to a single nucleotide base.
Subtypes: Substitution (base replaced), Insertion (base added), Deletion (base removed).
Frameshift Mutation:

Results from addition or deletion of nucleotides, shifting the reading frame.
Causes significant changes in amino acid sequence during translation.
Chromosomal Mutation:

Alters chromosome structure or number.
Examples: Duplication (segment copied), Deletion (segment lost), Inversion (segment reversed), Translocation (segment moved to another chromosome).

Question 19

Order the parts of a cell from biggest to smallest e.g cell to chromosome

Answer 19

Cell, Nucleus, Chromosome, Gene, DNA

Question 20

Explain how mutations can affect the chance of an organism’s survival (negative and positive)

Answer 20

Negative Effects:

Lethal Mutations: Cause death before or shortly after birth.
Deleterious Mutations: Harmful changes to proteins or regulatory sequences.
Reduced Fitness: Decrease in ability to compete, evade predators, or resist diseases.
Positive Effects:

Beneficial Adaptations: Provide advantages in specific environments.
Genetic Diversity: Contribute to adaptation to changing environments.
Evolutionary Innovation: Generate new traits or functionalities, driving diversification.

Question 21

What are the sides of the DNA strand called

Answer 21

Phosphate backboard

Question 22

What is a peptide bond

Answer 22

a chemical bond formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule

Question 23

explain the order of mRNA, tRNA, and rRNA and it’s function

Answer 23

mRNA (Messenger RNA) : It carries the instructions for making proteins from the DNA to the ribosomes.
tRNA (Transfer RNA) : It brings the building blocks (amino acids) to the ribosomes based on the instructions from mRNA.
rRNA (ribosomal RNA) : It helps in the assembly of amino acids into proteins at the ribosomes.

Question 24

What is the interphase

Answer 24

Interphase is the preparatory phase of the cell cycle where cells grow, perform their regular functions, and replicate their DNA in three stages: G1, S, and G2. It’s a vital period for the cell’s growth, maintenance, and readiness for division. occurs before miosis and mitosis

Question 25

parts of a chromosome

Answer 25

The significant parts of a chromosome are the centromere, telomeres, and chromatids.

Question 26

What does it mean if a chromosome is homologous

Answer 26

Homologous chromosomes are pairs of chromosomes in a diploid organism that have similar genes, although not necessarily identical.

Question 27

When does crossing over occur in meiosis

Answer 27

Crossing over, also known as genetic recombination, occurs during prophase I of meiosis. This is when homologous chromosomes pair up and exchange segments of their DNA, leading to the reshuffling of genetic material.