11 Inheritence Flashcards
Define inheritance
Transmission of genetic information from generation to generation
Define chromosome
thread-like structure of DNA, carrying genetic information in the form of genes
Define gene
length of a DNA that codes for a protein
Define allele
Versions of a gene
Define mitosis
nuclear division giving rise to genetically identical cells
How many pairs of chromosomes are there in humans
23 pairs
Define haploid
Containing a single set of unpaired chromosomes
Role of mitosis (4)
Repair of damaged tissues
growth
asexual reproduction
replacement of cells
Define diploid
Containing two sets of chromosomes
Define meiosis
reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells
How are gametes produced
Meiosis
gametes have single set of chromosomes. When the two gametes fuse, they become diploid cell with normal number of chromosome
Define genotype
genetic make-up of an organism in terms of alleles present
Define phenotype
observable features of an organism
Define homozygous
having two identical alleles for a particular gene
Define heterozygous
having two different alleles for a particular gene
Define dominant allele
allele that is expressed if present
Define recessive allele
allele that is only expressed when no dominant allele is present
Two types of phenotypic variation (2)
Discontinuous variation
continuous variation
What is discontinuous variation
characteristic can only have a limited number of specific phenotypes
Examples of discontinuous variation
sex, blood group, tongue rolling
What is continuous variation
where characteristic can have any value in a range
Examples of continuous variation
body weight, length of hair
Define variation
differences between indivudals of the same species
Causes of phenotypic variation
Environmental causes -
genetic causes -
What is discontinuous variation caused by
genetic variation
What is continuous variation caused by
genes
and
environment
Define gene mutation
change in gene or chromosome
Causes of mutation (2)
exposure of ionising radiation - EG: gamma rays, x-rays
chemical mutagens
Define natural selection
best adapted organisms having a better chance of passing on their genes to the next generation
Describe the process of natural selection (5)
In any population there is variation between individuals
organisms reproduce —> produce many offspring —> struggle for survival
offsprings have different combinations of variations from parents
Offsprings with adaptive features help them compete better for resources
Offsprings reproduce and pass on their alleles to the next generation
Define adaptation
process resulting from natural selection by wich populations become more suited to their environment over many generations
Describe evolution
chance in adaptive features of a population over time as a result of natural selection
Describe the development of strains of antibiotic resistance in bacteria
Describe selection breeding (2)
When a breeder chooses which parent organisms to breed together
selection of offspring showing the desirable features
Differences between natural selection and artificial selection (2)
humans decide on characteristics they want vs unpredictable as those most adapted to environment selected
Artificial selection are useful to humans while natural selection are better adapted to the environment
