B5.1 Flashcards
What is a gamete
A sex cell - egg/sperm
What is an allele
Different versions of the same gene
What is a phenotype
Visible characteristics of an organism
What are the causes of variation
Genetic material
Environmental factors
What is a genotype
Collection of alleles that determine characteristics
What is a genome
The entire genetic material of an organism
What is discontinuous variation
Characteristics that can be put into categories
What is an example of a discontinuous variation
Blood group, eye colour, sex
What is continuous variation
Variation that shows a wide range of values - can be measured
What are some examples of continuous variation
Height, weight, foot length
What do genetic and environmental variation combine to produce
Different phenotypes
What’s the cause of continuous variation
Genetic and environmental
What’s the cause of discontinuous variation
Genetic
What is asexual reproduction
A clone of an organism that is genetically identical to its parent
What organisms reproduce asexually
Bacteria - E-coli Potato plants Spider plants Daffodils Star fish
What is sexual reproduction
Involves two parents and the joining of male and female gametes during fertilisation
Why do plants produce sexually
To create a new seed
Advantages of sexual reproduction
- produces genetic material in the offspring
- species can adapt to new environments, due to variation - survival advantages
- disease is less likely to effect all the individuals in a population
What is a disadvantage of sexual reproduction
- requires two parents - slower
Advantages of asexual reproduction
- population can increase rapidly when conditions are favourable
- one parent needed
- more time and energy efficient
- faster
Disadvantages of a sexual reproduction
- no genetic variation
- species may only be suited to one habitat
- disease would effect all individuals in a population
What is fertilisation
When the nuclei of a female and make gamete fuse to create a zygote
What type of cell are gametes
Haploid - half the dna needed
What are the gametes in flowering plants
Pollen - male
Ovules - female
How are gametes made
Using meiosis
Describe the process of meiosis
- dna is replicated
- chromosomes pair up and line up on midline
- if chromosomes touch - parts of genetic material cross over - genetic variation
- spindle fibres contract - pull each chromosome to different sides
- cell divides in 2
Stage 2
- chromosomes are not copied
- pairs line up along midline
- spindle fibres contract - pull
- cell divides
What does meiosis form
Four separate cells with 23 chromosomes - genetically different
What’s the differences between meiosis and mitosis
Mitosis
- divides once
- produces 2 cells
- 46 chromosomes each
- used for new body cells
- happens in all parts of body
Meiosis
- divides twice
- produces 4 cells
- 23 chromosomes each
- used to make gametes
- happens in testes/ ovaries
