B5.1 Inheritance Flashcards
(29 cards)
What is meant by variation
Differences within a species
What is meant by phenotype
Characteristics which are observed in an organism
The appearance of an organism is called its phenotype
What are two causes of variation and what is meant by them
Genetic variation (variation caused by genetic material present in an organism that is inherited from their parents )
Environmental variation (variation caused by the environment in which you live)
What are examples of genetic variation
- eye colour
- blood group
- presence of a genetic disorder
What are examples of environmental variation
- language they speak
- where they live
- weight
- Learning
What is discontinuous variation
- characteristics which fall into distinct groups
- can only take results I’m specific (discrete) values
- displays genetic variation
- displayed as a bar chart
Examples:
- gender
- eye colour
What is continuous variation
- variation which can take any value between a minimum and a maximum
- can take any value within a range
- shows genetic and environmental variation
- displayed as a histogram ( with bars removed only line showing the trend)
Examples:
- leaf SA
- skin colour
- length of fur
What are diploid cells
Cells which contain two sets of chromosomes
There are 46 chromosomes in total
What are haploid cells
They have one of each chromosome
They only contain 23 chromosomes
What is a zygote
A fertilised egg
What happens during fertilisation
Two haploid gametes join together
This forms a diploid cell known as a zygote
The zygote divides many times by mitosis to produce a new organism
What is a genome
All of the genetic material present in an organism
Why are the combination of genes that an organism display unique
It is a mixture of both parents genetic material
How are gametes made
Meiosis - cell division which produces gametes
- 4 haploid cells are made from one diploid parent cell
What happens during meiosis
There are two main stages:
In the first stage :
1) chromosomes are copied
2) Chromosomes line up in the middle of the cells in pairs (1 from mother and 1 from father)
3) one member of each pair is pulled to opposite ends of the cell
4) the cell divides in two
5) two separate cells are formed
Stage 2:
6) chromosomes line up in the middle of the two new cells
7) each chromosome is pulled in half. A single copy of each chromosome is pulled to opposite ends of the cell
8) each cell divides in two, resulting in 4 haploid cells
What are alleles
Different versions of the same gene
What is a dominant allele?
Version of a gene whose characteristics is always expressed if present in the genotype
Only one dominant allele is needed for characteristics to be expressed
Shown by a capital letter
What is a recessive allele?
A version of a gene whose characteristics are only expressed if two copies are present in the genotype
Two recessive alleles are needed for the characteristic to be expressed
Shown by a lowercase letter
What is a genotype
The combinations of alleles present in an organism
What are the three main types of genotypes
Homozygous dominant - two copies of the same allele that are dominant (e.g BB)
Homozygous recessive - two copies of the same allele that are recessive (e.g bb)
Heterozygous - different alleles of a gene (e.g Bb)
What is a genetic cross
A technique used to show the possible characteristics of an offspring
What is a punnet square?
A diagram used to show the possible genetic makeup of offspring based on a mother and fathers genes
How are male chromosomes different to female chromosomes
The 23 pair of chromosomes is different depending on whether you are male or female
Female chromosomes have two large XX
Male chromosomes have one large C and one smaller Y chromosome
What is a mutation?
A change in the sequence of DNA bases
This can occur if DNA doesn’t replicate correctly
