L1 Genetics - biology Flashcards
DNA
- DNA stands for deoxyribonucleic acid
- DNA is in a form of a double helix/twisted ladder
- DNA is a self-replicating material that is present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.
- DNA is made up of nucleotides
Nucleotides
Nucleotides form the basic structural unit of DNA. Composed of sugar, a phosphate and a nitrogen base.
Four nitrogen bases:
Adenine (A) pairs with Thymine (T)
Guanine (G) pairs with Cytosine (C)
Allele
Different forms of the same gene. They can be either dominant or recessive.
- Allele determines phenotype
Phenotype
The observable characteristics of an individual resulting from its genotype.
Chromosome
Threadlike structure of DNA that contains genes and is found in the nucleus of a cell. It is made up of proteins and DNA organized into genes. Each cell contains 23 pairs of chromosomes.
Gene
A segment of DNA, coding for a protein that determines the trait/characteristic of an individual.
- Gene determines genotype
Genotype
The two alleles available in the individual
- Homozygous OR heterozygous
Protein
Protein are large, biologically important polymers comprised of sequences of amino acids
Trait
A genetically determined characteristic or condition. Traits can be determined by genes or the environment.
e.g fin length, body shape, eyesight, etc
Advantages and disadvantages of sexual reproduction
Advantages
- There is a variation as the offspring will carry the alleles from both parents mixed together.
- Offspring will most likely be more protected
Disadvantages
- Time-consuming as you need to find a partner
- Takes longer than asexual reproduction
Amino acid
Amino acids are small molecules that are the building blocks of proteins.
Difference between sexual and asexual reproduction
Sexual Reproduction
- Involves two parents and produces offspring that are genetically unique.
Asexual reproduction
- Only involves one parent and produces offspring that are genetically identical to each other and to the parent.
Advantages and disadvantages of asexual reproduction
Advantages
- Organisms do not need to find partners, therefore is less time-consuming.
Disadvantages
- No variation which means any negative mutation or changes will be passed on to offspring.
Short lifespan
Variation
The difference between individuals which is genetically inherited
Genetic variation
Mutagens cause genetic variation
Diploid
Diploid are two copies of every chromosome
Environmental factors
Any factor that influences es living organisms.
- Sound, light, parasites, temperature
Zygote
The name of the first cell created by fertilisation
Gametes
Specific names for sex cells Female gamete - Egg Male gamete - Sperm
Haploid
Haploid are cells that have a single set of chromosomes
Mitosis
Type of division used to produce
Meiosis
Type of division used to produce cells (gametes)
Homozygous
pairs of chromosomes that code for the same characterisitic
Heterozygous
Having two different alleles of a particular gene/genes
Recessive
The allele is always expressed when no dominant allele is present (homozygous recessive)
- Expressed through lower case letters (a,b,c)
Dominant
The allele is always expressed when present
- Expressed through capital letters (A, B, C)
Mutation
A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.
Causes of mutation
- DNA copying mistakes during cell division
- Exposure to radiation (e.g x-rays)
- Exposure to chemicals (mutagens)
- Infection to viruses
Examples of mutation
- Cystic fibrosis
- Down syndrome
- ## Sickle-cell anemia
Types of mutation
Gene mutation
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