B6 - Inheritance, Variation And Evolution Flashcards
(22 cards)
What is DNA?
A polymer made up of two strands coiled into a double helix.
What are chromosomes?
Long molecules of DNA that normally come in pairs.
How many pairs of chromosomes do humans have?
23 pairs
The 23rd pair carries gens which decide a persons sex.
What is a gene and what does each gene code for?
A small section of DNA found on a chromosome.
Codes for a particular sequence of amino acids which are put together. To make a specific protein.
What is a genome?
An organisms entire set of genetic material.
What is the human genome?
- Genes linked to disease can be identified.
- This helps us better understand inherited diseases, so we can develop effective treatments.
- Tiny differences in peoples genome can be studied.
- This helps us trace the migration patterns of past human populations.
What is a mutation?
Changes to the sequence of DNA based. They occur continuously.
What is asexual reproduction? (3)
- One parent
- Mitosis
- Genetically identical offspring
What is sexual reproduction? (3)
- Two parents
- Meiosis and mitosis
- Offspring containing a mixture of the parents genes.
What are the advantages of asexual? (2)
Fast - so many identical offspring can be produced in favourable conditions
Only one parent needed so no energy wasted finding a mate.
What are the advantages of Sexual?(2)
Variation in offspring increases the chance that some individuals of a species will survive a change in the environment.
Can use selective breeding to utilise the variation in offspring and increase food production.
What is meiosis? (4)
- Cell duplicates
- Cell divides and each new cell has one copy of each chromosome.
- Both cells divide again to make four gametes.
- Each gamete only has a single set of chromosomes.
What does allele mean?
A version of a gene
What is dominant?
An allele that is always expressed
What is recessive?
An allele that is only expressed when two copies are present.
What is a genotype?
An organism’s combination of alleles.
What is a phenotype?
Characteristics an organism has
What is Polydactyl? What is it caused by?
A genetic disorder where a baby’s born with extra fingers or toes.
It’s caused by a dominant allele.
What are the arguments against embryonic screening? (2)
- Expensive
- Might want to screen embryos so they can pick the most ‘desirable’ one.
What is selective breeding?
Breeding plants or animals for particular characteristics.
What are the uses of selective breeding? (3)
- Greater meat or milk production
- A good temperament in dogs
- Disease resistance in crops
