INHERITANCE Flashcards
(22 cards)
What is a MUTATION
A random change in the DNA sequence of a gene that can sometimes lead to a change in the protein that the gene codes for.
MUTATIONS are continuous, and can be inherited
What are ALLELES
ALLELES are variations of the same gene
What is a PHENOTYPE
The observable characteristics of an organism
What is a GENOTYPE
The combination of alleles that control each characteristic
HOMOZYGOUS definition
If two alleles of a gene are the SAME (AA, bb)
HETEROZYGOUS definition
If two alleles of a gene are DIFFERENT (Aa, Bb)
CODOMINANCE definition
When two alleles are expressed in the same phenotype
What is POLYGENIC INHERITANCE
When a characteristic is controlled by two or more genes interacting together, rather than a single gene
What are PEDIGREE CHARTS
-diagram representing the family history of a genetic condition
What are MONOHYBRID CROSSES
Diagrams that show us the possible combinations of alleles, of a characteristic controlled by a single gene, that could be inherited in the offspring.
How does the inheritance of sex work
Females have a homologous pair of XX chromosomes, and can only pass down X alleles
Males have an x and a Y chromosome, and can pass down either X or Y alleles
-there is a 50 % chance of male or female in offspring always and it depends on the male’s sperm.
DIPLOID CELLS
Cells with 2 copies of each chromosome
-cells with 46 chromosomes
What is MITOSIS
MITOSIS is a from of cell division that produces two daughter cells that are GENETICALLY IDENTICAL to the parent cell
The process of mitosis
PMAT (i) :
1)PHROPHASE:
-The chromosomes in the nucleus duplicate to form CHROMATIDS,
-the nuclear membrane begins to break down
2)METAPHASE:
-the chromatids line up at the centre of the cell
3)ANAPHASE:
-the chromatids are separated to form the chromosomes for the 2 daughter cells
-the separated chromatids are pulled to opposite ends ‘poles’ of the cell.
4)TELOPHASE:
-New nuclei begin to form at the poles of the cell around the chromosomes
-The cell cytoplasm begins to divide- called CYTOKINESES
+ INTERPHASE: the time between divisions
What is MEIOSIS
MEIOSIS is a type of cell division which produces 4 genetically different daughter cells (haploid gametes)
What is MITOSIS used for?
-GROWTH
-Repair
-Asexual reproduction
Ex: layers under the skin surface are constantly dividing by mitosis to repair and replace killed skin cells
Describe the process of MEISOSIS:
MEIOSIS occurs in two stages: MEIOSIS I + MEIOSIS II
MEIOSIS I:
1) chromosomes in the nucleus duplicate to form chromatids and the nuclear membrane begins to break down
2) maternal and paternal pairs join and line up at the centre of the cell
3) parts of the DNA are swapped between maternal and paternal chromosomes to form RECOMBINANT CHROMOSOMES
4) the maternal + paternal pairs are separated and pulled to opposite ends of the cell
5) the first cell division occurs
MEIOSIS II:
1)the two chromatids of each chromosome seperate in the daughter cells and are pulled to opposite ends of their cells
2) second cell division occurs forming 4 haploid gametes
DIFFERENCES between MITOSIS + MEIOSIS:
-haploid vs diploid
-4 daughter cells vs 2 daughter cells
-genetically identical vs genetically different
-one cell division occurs vs two cell divisions
Explain Darwin’s theory of NATURAL SELECTION:
1) there is GENETIC VARIATION in all offspring
2) there is COMPETITION between all offspring (mates, food, resources) or changing conditions in the environment (selection pressure) favours one particular form of species (selective advantage)
3) offspring with the most ADVANTAGEOUS characteristics survive and the others die (survival of the fittest)
4) the surviving offspring are more likely to reproduce and can then pass on their advantageous alleles to their offspring
5) over many generations, the advantageous traits become more common in the population
Adaptations of the polar bear:
-thick layer of white fur, reduces heat loss and acts as camouflage in the snow
-wide, large paws- increase surface area and reduces pressure when walking in the snow, are used for swimming
-strong, muscular legs- allows them to swim for days in the artic ocean
-a large body mass- small SA: V ratio, which reduces heat loss
-10cm thick layer of insulating fat- reduces heat loss
-bumps on the pads of the paws- provides grip on the ice
Explain how ANTIBIOTIC resistance in bacteria works
1) sometimes random mutations of the bacteria can cause antibiotic resistance,
2) the resistant bacteria then survives while the others die
3) the antibiotic resistant bacteria can then reproduce by mitosis and pass on the allele for antibiotic resistance
4) since bacteria reproduces rapidly, there will be a fast increase in antibiotic resistant bacteria across the population