Genetics Flashcards
Describe the overall structure of DNA.
DNA consists of two strands coiled together to form a double helix.
What are the three components of a DNA monomer?
A DNA monomer (nucleotide) consists of:
* A sugar (deoxyribose)
* A phosphate group
* A nitrogenous base.
What are the four nitrogenous bases found in DNA?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
How do the nitrogenous bases hold the two DNA strands together?
Through base pairing:
* Adenine (A) pairs with Thymine (T)
* Cytosine (C) pairs with Guanine (G)
How many strands does RNA have?
One strand.
What type of sugar is found in RNA?
Ribose.
What are the four nitrogenous bases found in RNA?
- Adenine (A)
- Uracil (U)
- Cytosine (C)
- Guanine (G).
Define a gene.
A segment of DNA occupying a specific location on a chromosome that codes for a protein.
Define an allele.
Different forms of the same gene.
In rats, black fur (B) is dominant to grey fur (b). What does the genotype BB represent?
Homozygous dominant (black fur).
In rats, black fur (B) is dominant to grey fur (b). What does the genotype Bb represent?
Heterozygous dominant (black fur).
Define a chromosome.
A strand of DNA carrying genes.
Define a gene.
A length of DNA on a chromosome that codes for a specific protein (a sequence of bases of DNA that codes for a sequence of amino acids).
Define phenotype.
An observable feature of an organism.
Define genotype.
The allele combination an organism has (e.g., AA, Aa, or aa).
Define a dominant allele.
The form of a gene that is expressed in the phenotype of a heterozygous genotype.
Define a recessive allele.
The form of a gene expressed in the phenotype only in the absence of a dominant allele.
Define codominance.
- A case where two alleles are neither dominant nor recessive to each other, and both are expressed in the phenotype.
- The offspring shows a different phenotype than either parent.
Give an example of codominance in human blood groups.
IA = Group A, IB = Group B, IO = Group O.
What is polygenic inheritance?
A phenotype controlled by more than one gene, resulting in continuous variation.
Briefly describe transcription.
DNA unzips and unwinds, and the sequence of bases of DNA is copied into mRNA.
Briefly describe translation.
- mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm.
- tRNA with an anticodon brings a specific amino acid, and amino acids bind together to form a protein molecule.
Define mutation.
A change in the sequence of bases in DNA, resulting in a change in the sequence of amino acids in a protein molecule, causing a change in the shape and function of the protein.
How does mutation lead to variation within a species?
Mutation introduces new alleles, which can result in different traits.
How does natural selection occur?
Individuals with favorable alleles survive and reproduce at a higher rate, increasing the number of individuals with those alleles in the population.
Give an example of natural selection.
The development of antibiotic resistance in bacteria.
Describe the key features of mitosis.
Produces 2 daughter cells, which are diploid and identical to the parent cell.
Example: growth/repair.
Describe the key features of meiosis.
Produces 4 daughter cells, which are haploid and not identical to the parent cell.
Example: production of gametes.
