2.5 Genetic Variation Flashcards
Gene
section of DNA that codes for a protein that influences a characteristic/ trait
Traits
The physical expression of genes as characteristics
Sexual reproduction
The creation of new living organisms by combining genetic information from two parent organisms
Asexual reproduction
Asexual reproduction occurs when an organism makes more of itself without exchanging genetic information with another organism through sex.
Binary fission
A single parent cell divides into two daughter cells
Locus
Position of a gene on a chromosome
Homologous chromosomes
A pair of chromosomes with one maternal and one paternal. They have genes that control the same trait at the same locus
Alleles
Different forms of a gene eg. blue or brown eyes
Homozygous dominant
An organism that has two dominant alleles for a gene
Heterozygous
An organism that has both versions of an allele and the dominant allele will be expressed
Homozygous recessive
An organism that has two recessive alleles for a gene
Genome
All of the genetic material within an organism
DNA
A molecule composed of many nucleotides with a sugar-phosphate backbone. Two DNA polymers coil around each other to form a double helix carrying genetic instructions for the life processes of all known organisms
Nucleotide
A single unit of DNA
Name the three parts of a nucleotide
A deoxyribose sugar, a phosphate group, and one of four nitrogenous bases (A, T, C, G)
Chromosome
A long DNA molecule with part or all of the genetic material of an organism
The genotype of an organism
The two alleles an organism posses for a trait eg. Aa
The phenotype of an organism
The observable characteristics of an organism due to their genotype
Inheritance
The passing down of genetic information from one generation to the next
Meiosis
A type of cell division that produces gametes
Gametes
Sex cells
Eukaryotes
Organisms whose cells contain a nucleus
Diploid cell
Cells that contain an entire set of chromosomes inherited from both parents
Haploid cell
Cells that only have a single set of chromosomes
Fertilisation
When one gamete (eg. sperm cell) fuses with another gamete (eg. egg) to form a single zygote
Zygote
A diploid cell resulting from the fusion of two haploid gametes
Punnett squares
Simple diagrams that show the possible allele combinations that can occur when two parental gametes are fertilised
Mutations
A permanent change in an organism’s genetic material
Gametic mutations
Mutations that can be passed down to offspring, as they occur within the cells of testes/ ovaries and therefore present in gametes
Centromere
Joins two sister chromatids
Sister chromatid
A copy of the original chromosome when it has been replicated
Why is meiosis important?
Meiosis produces gametes that can be fertilised to create a new individual. Meiosis maintains the chromosomal number from generation to generation and promotes genetic diversity/ variation in the population
Phenotypic variation
The differences in physical features (traits) within a population
Genetic variation
The number of different alleles within a population
Mutagens
The factors that cause mutations
Where does meiosis occur?
Meiosis occurs in specialised germ cells found within sex organs
Disjunction
The process during meiosis when chromosomes are pulled apart by spindle fibres
Spindle fibres
Structures that form during cell division to separate sister chromatids
Point mutations
Mutations that cause one or very few nucleotides in a sequence
Chromosomal mutations
Mutations involving a long segment of DNA
Random fertilisation
Egg and sperm cells combine randomly with many different possible combinations
Non-heritable/ acquired variation
Variation in an individual that can not be passed onto offspring, and usually occur due to environmental factors
Why is genetic variation important?
Variation ensures that if conditions change (eg. climate, resources, disease, etc.) some individuals will have adaptations that enable them to continue surviving and reproducing. This ensures the survival of a species.
