3B Inheritance Flashcards
What is the genome?
All of the genes present in an organism
What is a gamete?
Gametes are sex cells (sperm or eggs)
What is a chromosome?
Tightly packaged DNA
How many chromosomes do human body cells have?
46 chromosomes (23 pairs)
How many chromosomes do human gametes have?
23 chromosomes
Where are chromosomes located?
In the nucleus of the cell
What is a gene?
A section of DNA that codes for a protein
What is an allele?
Different versions of the same gene
What is a dominant allele?
A version of a gene where only one copy is needed for it to be expressed
What is a recessive allele?
A version of a gene where two copies are needed for it to be expressed
What is meant when an organism is homozygous?
Has two copies of the same allele
What is meant when an organism is heterozygous?
Has two different versions of the same gene (one dominant and one recessive)
What is the genotype?
The genes present for a trait
e.g Aa
What is the phenotype?
The visible characteristic
What is monohybrid inheritance?
The inheritance of one allele
Things to include in punnet squares
- Alleles (and person that carries it)
- Ratio / Percentage
What do family pedigrees show?
The inheritance of an allele over generations
3 processes that require mitosis
- growth
- repair
- asexual reproduction
How many cells does mitosis produce
One parent cell produces two daughter cells.
How many cells does meiosis produce?
One parent cell produces 4 daughter cells
2 differences between mitosis and meiosis
- Mitosis produces 2 genetically identical cells whereas meiosis produces 4
- Mitosis produces diploid cells whereas meiosis produces haploid cells
What is random fertilisation?
- The random chance of fertilising a specific sperm with a specific egg
- This increases variation as any female can mate with any male and any one of the millions of sperm could fertilise the egg
What are the two types of variation?
Genetic variation and environmetal variation
2 traits in humans caused only by genetic variation
- Eye colour
- Blood type
2 traits in humans caused by a mix of environmental and genetic variation
- Height
- Weight
What is a mutation
A random change in the genetic material of an organism
Natural selection
- There is variation in “specific characteristic”
- The mutation with “” provides a selective advantage in “ “
- The organism with the mutation “” survives
- reproduces and pass on the alleles
Define evolution
Evolution is a change in the genetic makeup of a population over time due to natural selection
Describe how anitbiotic resistance arises
- A random genetic mutation causes a bacterium to become resistant to the antibiotic
- When the antibiotic is used, all the bacteria that do not have the mutation are killed
- The population containing just the resistant bacteria mutation then begins to grow
