Genetics y11 Flashcards
DNA
A molecule/chemical that carries genetic information in the form of a code
Chromosome
A thread-like structure made up of long lengths of DNA
Gene
A gene is a section of DNA that codes for a protein that determines a particular trait
Allele
A different form of a gene
Gamete
A sex cell
Fertilisation
The fusion of 2 gametes
Foetus
An unborn offspring developed beyond a embryo
Homologous chromosome
Homologous pair of chromosomes that have the same genes in the same loci
Meosis
The type of cell division gametes are made by
Mitosis
The type of cell division body cells are made by
Sexual reproduction
Reproduction where 2 individuals genetically contribute to the offspring
Asexual reproduction
Reproduction where only one individual genetically contributes to the offspring.
Genetic variation
The differences (in DNA) of individuals in a population/species.
Genetics
Genetics is the study of the variation and inheritance of genes
Genetic code
It is the base sequence of DNA
Mutation
A random and permanent change in the base sequence/genetic code of DNA.
Point mutation
A single base or very few bases are affected and only affect one gene.
Explain the differences between a gene and an allele
A gene is a section of DNA that codes a protein for a specific trait whereas an allele is a different version of a gene. Members of the same species all carry the same genes but may carry different alleles.
Eg. Humans all have a gene that codes for eye colour however what the eye colour is, is determined by an allele. Gene - Eye colour Allele- Blue, Black, Green etc.
Structure of DNA
Double Helix
Nucleotide
Phosphate (circle) -> deoxyribose sugar (pentagon) -> nitrogen base
Rosalind Franklin
In 1953 due to her X-ray diffraction work, she was able to create photo 51. This helped deduce the double helix structure of the DNA
Draw homologous chromosome
() ()
o <– Centromere
() ()
Sister chromatids/Non-sister chromatids.
What do individuals inherit from both parents?
Individuals inherit 2 copies of each chromosome; one chromosome from each parent. Therefore each individual carries 2 copies of each gene (one from each chromosome they inherit). Homologous chromosomes may carry different alleles.
Non-sister chromatids carry different alleles
Sister chromatids carry the same alleles.
Genetic code is….
Genetic code is the base sequence of DNA and read in triplets. Each triplet codes for an amino acid. These amino acids are ordered according to the base sequence to form different proteins. Therefore different base sequences produce different proteins.
2 different sources of genetic variation
Mutations and sexual reproduction
Mutation is the only
Source of new alleles/ new genetic variation in a population
How do mutations cause variation
Mutations cause variation because any change in a base sequence results in a different protein being formed resulting in a different alleles in a gene. These differences in alleles cause differences in DNA causing variation…..
Point Mutation
A point mutation is when only a single bases or a few bases are affected or altered. Therefore this only affects one gene.
1. Deletion } Results in frame shift
2. Insertion } which is most likely fatal
3. Substitution
Relating point mutation w diseases
Cystic fibrosis - Increase mucus production
Sickle Cell- Moon shaped blood cells, less oxygen
Haemophillia (Sex linked) - X chromosome; more likely in men, clotting issues.
Down syndrome-
BRCA1/2 - Cancer risk.
Sexual Reproduction
When 2 individuals genetically contribute to create an offspring that is genetically different from them. It is a source of variation.
Asexual Reproduction
When only one individual genetically contributes to the offspring. The offspring is a clone/genetically identical to the parent ie. no variation.
Advantages and Disadvantages of Sexual and Asexual reproduction
SA- Source of genetic variation
AA- Fast
SD- Slow
AD- No genetic variation
How does fertilisation produce variation?
Fertilisation is the fusion of 2 gametes. These 2 gametes come from 2 different individuals and it is completely random as to which gametes come together. This means that fertilisation
