Unit 2B Flashcards
Characteristics
Features such as eye colour, which are determined by proteins made by genes.
We inherit different combinations of chromosomes (and therefore genes) from our parents, making us unique.
Karyotype
The pattern made by breaking open the nucleus of a cell and lining the chromosomes up in matching pairs.
Fertilisation (human)
Occurs when the nucleus of an egg (23 chromosomes) combines with the nucleus of a sperm (23 chromosomes) to create a zygote (46 chromosomes).
Alleles
The different versions of a gene. eg. the eye colour gene has 3 alleles - brown, green and blue
The 2 chromosomes in a pair carry the same gene, but the alleles may be different.
Genotype
A 2 letter code indicating which alleles you have inherited from each parent (for a single gene) eg. BB
Capital letter = dominant allele, lower case letter = recessive allele.
Phenotype
Describes how a gene is expressed.
Often appearance (eg. eye colour) but not always (eg. blood type).
Monohybrid cross
Used to study how the alleles of 2 parents recombine in the offspring, for a single gene.
eg. BB x bb
Punnett square
A table used in a monohybrid cross to recombine gametes.
F1 generation
The offspring created in the original cross.
F2 generation
The offspring created by breeding 2 members of the F1 generation together.
Continuous variation
Variation that is controlled by many genes.
Produces a range of data. eg. height which can be displayed as a histogram.
Discrete (discontinuous) variation
Variation that is controlled by a single gene.
Data falls into separate categories eg. blood type, tongue rolling and is displayed as a bar chart.
Annual plants
Complete their lifecycle in one year. eg. poppies
They survive the winter as dormant seeds which germinate in the spring.
They are small, fast growing, produce many lightweight seeds and can grow on poor soils.
Perennial plants
Do not die after one year - they regrow from existing plants. eg. trees
They grow slowly, producing large seeds. They can grow very tall over time, and need fertile soil.
Plant growth curve
Shows the change in dry mass of a plant over its lifecycle.
Mass decreases during germination as the food store is used up, increases when the plant carries out photosynthesis and grows new tissue, then decreases as seeds are shed.