B6: inheritance Flashcards
(20 cards)
Describe the differences between sexual and asexual reproduction
SEXUAL:
- involves fusion of male and female gametes: fertilisation
- offspring receive genetic material from both parents
- variation in offspring
ASEXUAL:
- doesn’t involve gamete as there is only one parent
- no mixing of genetic material
- offspring are genetically identical (clones)
- only involves mitosis, not meiosis.
How does meiosis halve the number of chromosomes in gametes?
- All of the chromosome pairs are copied
- The cell divides in two
- Now both cells divide one more time to form gametes, with single chromosomes.
- produces four different gametes from one cell, which are different. They each have different alleles.
How does fertilisation restore the full number of chromosomes?
Because the two gametes fuse together, they add up to make 23 chromosome pairs.
Where does meiosis take place?
Only in the reproductive organs
Describe the structure of DNA
- consists of two strands, which is a polymer
- the two strands wrap around each other to form a double helix
What is a genome?
The entire genetic material of an organism
Why is it important we understand what a genome is? (3)
- help search for genes linked to a diseases (eg. Cancers)
- help us understand and treat inherited disorders (eg. Cystic fibrosis)
- can trace human migration patterns of the past
What is a gene?
A small section of DNA on a chromosome
What is a dominant allele?
An allele will show in the phenotype even if there is only one copy present.
What is a recessive allele?
An allele will only show in the phenotype if two copies are present.
What is an allele?
Versions of a gene
What is homozygous?
Two copies of the same allele
What is heterozygous?
Two different alleles
What is a genotype?
Tells us the alleles present
What is a phenotype?
Characteristics caused by the person’s alleles
Which allele expresses cystic fibrosis?
Cystic fibrosis is expressed in the recessive allele
Describe polydactyly
Having extra fingers or toes.
What is the issue around embryo screening?
- expensive, money should be used elsewhere
- often large number of embryos are created but only a small number are implanted. Some think this is unethical
- in future, we may be able to chose desirable offspring. Some find this unethical.
Which allele expresses polydactyly?
Dominant
Which set of sex chromosomes do males and female have?
- Male: XY
- Female: XX