Genetics And Reproduction (B13-15) Flashcards
(25 cards)
What type of cell division produces gametes?
Meiosis.
Meiosis occurs in ovaries and testes, halving the chromosome number from diploid to haploid.
How many gametes are formed at the end of meiosis?
4 gametes
Each gamete has half the chromosomes and is genetically different.
What is fertilisation?
Fusion of male and female gametes
It restores the full number of chromosomes and results in a zygote.
What is the structure of DNA?
Double helix made of nucleotides
Nucleotides consist of phosphate, sugar, and base.
What are the four bases of DNA?
A, T, C, G
Adenine pairs with Thymine, and Cytosine pairs with Guanine.
What is a genome?
Entire genetic material of an organism
The human genome has around 3 billion base pairs.
What is a gene?
A small section of DNA that codes for a specific protein
The order of bases determines the order of amino acids in a protein.
Define alleles.
Different forms of the same gene
Example: Dominant allele (B) and recessive allele (b).
What is the difference between genotype and phenotype?
Genotype: genetic makeup; Phenotype: physical expression
Example: Genotype Bb; Phenotype brown eyes.
What are Punnett Squares used for?
To predict genetic crosses
They show probabilities of offspring inheriting traits.
What causes Cystic Fibrosis?
A recessive allele
It affects cell membranes, causing thick mucus in lungs.
What is Polydactyly caused by?
A dominant allele
It results in extra fingers or toes.
What is a carrier?
Someone who has one copy of the recessive allele but doesn’t have the disorder
Carriers can pass the allele to offspring.
What do family trees (pedigrees) track?
Inheritance of traits through generations
They illustrate how traits are passed down.
How is sex determined in humans?
By X and Y chromosomes
XX = female, XY = male.
What is variation?
Differences in individuals of the same species
Caused by genetic and environmental factors.
What is a mutation?
A change in the DNA
Most mutations have no effect; some are beneficial or cause disorders.
What is natural selection?
Theory by Charles Darwin
Individuals with beneficial traits survive and reproduce, passing on advantageous genes.
What are the steps of natural selection?
- Variation exists
- Some have advantageous traits
- Better survival and reproduction
- Trait becomes more common
This process leads to evolution over generations.
What is selective breeding?
Humans choose desired traits and breed those individuals
It can lead to reduced gene pool and increased risk of genetic disorders.
What is genetic engineering?
Modifying the genome of an organism by inserting genes from another organism
Examples include producing insulin in bacteria and GM crops.
What does extinction mean?
When no individuals of a species remain
Causes include new predators, disease, competition, and environmental changes.
How do fossils provide evidence of past life?
They form from hard parts not decaying or preservation in ice/amber
Fossils also result from gradual mineral replacement.
What defines asexual reproduction?
Involves only one parent and produces genetically identical offspring
Common in bacteria and certain plants.
