Inheritance Flashcards
Define a gene
A gene is a unit of inheritance with a specific sequence of nucleotides as part of a DNA molecule containing information to synthesise a polypeptide
Define an allele
An allele is an alternative form of a gene
What is a dominant allele
An allele that can always be expressed in the phenotype
What is homozygous dominant
Having 2 identical dominant alleles
What is heterozygous
Having 2 different alleles
What is a recessive allele
An allele that can be expressed in the phenotype when it is homozygous
What is homozygous recessive
Having 2 identical recessive alleles
Define genotype
Genotype is the genetic makeup of an organism
Define phenotype
Phenotype is an observable trait of an organism
Define codominance
Codominance is when both alleles have equal effect on the offspring, so both alleles are expressed in the phenotype
Define monohybrid inheritance
Monohybrid inheritance is the inheritance of a single characteristic
How is genotype linked to phenotype
Phenotype is the expression of the genotype in a tangible form
What is Mendel’s Law of Segregation
Mendel’s Law of Segregation states that genes occur in pairs and that each gamete only receives 1 allele of each pair, so the 2 alleles of the organism are separated into different gametes to ensure variation
What are male sex chromosomes
XY
What are female sex chromosomes
XX
Define sex linkage
Sex linkage is the carrying of genes on sex chromosomes
In a pedigree, what are males and females represented by
Male - square
Female - circle
What are autosomes
Homologous chromosomes except sex chromosomes
Define variation
Variation is the differences in traits between individuals of the same species
What types are variation are there
- Continuous variation
- Discontinuous variation
What are some causes of variation
Genetic factors
- Chromosome and gene mutation
- Random fertilisation of gametes
Environmental factors
Describe continuous variation
- Range of phenotypes
- Greatly affected by environmental conditions
- Controlled by many genes
Describe discontinuous variation
- A few clear-cut phenotypes
- Relatively unaffected by environmental conditions
- Controlled by just 1 or a few genes
Define evolution
Evolution is the change in heritable characteristics of biological populations over successive generations
What is Darmin’s theory of evolution
Darwin’s theory of evolution states that all organisms arise and develop through natural selection
What are the principles of natural selection
- Variation
- Heredity
- Overproduction
- Limited resources
- Fitness
- Genetic composition
Describe how natural selection works
- Variation within population caused by spontaneous mutation
- Only fittest will survive
- Those with genetic variation best adapted to environment more likely to survive till maturity
- Higher chance of reproducing and passing down desirable genes to offspring
What are some environmental factors that act as forces of natural selection
- Amount of water and food
- Living space
