Genetics and reproduction

Question 1

The aim of reproduction is…

Answer 1

To perpetuate the hereditary characteristics of a species, and to mix up DNA to ensure better chances of a species’ survival

Question 2

DNA structure

Answer 2

Double helix containing nitrogenous bases, ribose sugars, and phosphate groups

Question 3

Nitrogenous bases

Answer 3

Adenine and thymidine

Guanine and cytosine

Question 4

Chromosomes are…

Answer 4

Two long strands of DNA, one maternal and one maternal, each called a chromatid

Question 5

DNA to protein

Answer 5

1. DNA unravels and is transcribed to mRNA
2. mRNA carries protein code to ribosome
3. tRNA decodes mRNA message by presenting an anti-codon and linking corresponding amino acids together

Question 6

A gene is…

Answer 6

A segment of DNA that codes for a specific protein and is responsible for a specific phenotype/trait

Question 7

Mendel’s Law of Segregation

Answer 7

Pairs of traits (alleles) separate during gamete formation and randomly re-unite on fertilisation

Question 8

Mendel’s Law of Independent Assortment

Answer 8

Trait pairs separate independently during gamete formation, i.e. traits are transmitted to offspring independently of one another

Question 9

Genotype vs phenotype

Answer 9

Genotype is genetic make-up

Phenotype is an observable characteristic

Question 10

Inherited vs familial

Answer 10

Inherited is genetic information given from the parents

Familial is a phenotype seen in two or more family members which may or may not have a genetic basis

Question 11

Alleles are…

Answer 11

Genes that contain different descriptive data about the same trait

Question 12

Homozygous vs heterozygous

Answer 12

Homozygous means that two genes received from the parents are the same, heterozygous means they are different

Question 13

Types of allele

Answer 13

Dominant, recessive, and incompletely dominant (influenced by other genes)

Question 14

Overdominance is…

Answer 14

When a heterozygous allele pair have enhanced characteristics compared to a homozygous pair, e.g. malarial resistance in heterozygous sickle cell carriers

Question 15

Co-dominance is…

Answer 15

When two alleles are equally dominant, e.g. in blood groups

Question 16

Genetic disorders (3)

Answer 16

1. Single gene/Mendelian - common
2. Polygenetic/multi-factorial complex diseases, e.g. diabetes type II
3. Chomosomal conditions, e.g. Down’s syndrome

Question 17

Epistasis

Answer 17

The ability of one gene to affect the function of another, e.g. diabetes mellitus is an epistatic illness involving up to 7 genes

Question 18

Pleotropism is…

Answer 18

When a gene has more than one effect

Question 19

Polymorphisms are…

Answer 19

Commonly occuring variants of an allele in a specific population (e.g. an ethnic group)

Question 20

Mitosis is…

Answer 20

Non-reproductive cell division, resulting in two identical daughter cells
Diploid cells with 23 pairs of chromosomes identical to parent cell

Question 21

Process of mitosis

Answer 21

Interphase - DNA doubles
Prophase - nuclear membrane breaks down, centriole spindle formation begins
Prometaphase - chromosomes attach to spindles
Metaphase - chromosomes align at the equator of the cell
Anaphase - duplicate chromosomes are separated by spindles shortening
Telophase - chromotids reach poles and cells pnch into two at the equator

Question 22

Meiosis is…

Answer 22

Reproductive cell division, resulting in 4 daughter cells (haploid) with 23 chromosomes each

Question 23

Process of meiosis

Answer 23

Prophase I - nuclear membrane breaks down, ‘crossover’ where DNA is exchanged between chromatids
Metaphase I - chromosomes align at the equator
Anaphase I - chromosomes are pulled to each pole
Telophase I - cell pinches to create 2 sister cells
Meiosis II - mitotic division, but DNA does not replicate