DNA Flashcards
What are DNA molecules?
Large and complex molecules which carry the genetic code that determine the characteristics of a living organism
What are genes
A gene is a section of DNA that codes for a specific protein
Unit of heredity
What is a chromosome
A thread-like, gene carrying structure made of protein and DNA by which hereditary information is physically passed from one generation to the next
How many chromosomes do we have?
23 pairs
What is a genome
Entire DNA of an organism
What is a homologous pair
A pair of chromosomes, one from each parent, containing similar values
What are alleles
Different versions of the same gene
Only one allele is expressed
What is a genotype
The collection of alleles that determine the characteristics and can be expressed as a phenotype
Name the nucleotides
Adenine, guanine, thymine, cytosine
What is a nucleotide
A building block of DNA consisting of 5 covalently bonded sugars to an organic gas and phosphate group
Complementary base pairing
Adenine and thymine - 2 hydrogen bonds
Cytosine and guanine - 3 hydrogen bonds
Differences between RNA and DNA
RNA = single stranded
Contains uracil instead of thymine
RNA contains ribose, DNA contains deoxyribose
Name the 2 types of RNA
mRNA - messenger RNA
tRNA - transfer RNA
What does mRNA do
Forms a copy of the DNA code
What does tRNA do
Carries amino acids to ribosomes
Describe transcription
DNA double helix unwinds
Free RNA nucleotides complimentary base pair with the template strand
Polymerised (by RNA polymerase) to form mRNA
Double helix will rewind
mRNA moves to next step
Describe translation
- mRNA strand travels through cytoplasm and attaches to ribosome
- Codon of mRNA complimentary base pairs with anticodon of tRNA
- tRNA molecules transport specific amino acids to the ribosome which they leave behin shortly after lining up opposite DNA
- Used tRNA molecules exit ribosome and collect another specific amino acid
- A chain of several hundred amino acids in correct order according to the original DNA is then made - called polypeptide
What is a mutation
An alteration in the nucleotide sequence of the genome of an organism
What is duplication
Nucleotide is underrated twice instead of once
Entire base sequence is altered
What is deletion
Nucleotide is missed out
Entire base sequence is altered
Whole gene is different
What is substitution
Different nucleotide is used
Codes for different amino acid
Significant alteration in the functionality of a protein or total lack of function may occur
What is an inversion
Sequence of the bases in a triplet is reversed
Effects similar to substitution
Only one triplet is affected
Factors that increase the likelihood of mutations:
1) sunlight and skin damage (UV radiation)
2) smoking (distorts shape of DNA molecule)
3) ionising radiation (gamma rays and X-rays)
Homozygous
Both alleles present are the same
Heterozygous
Both alleles present are different
Genotype
What alleles are present in an organism
Phenotype
‘Outward’ expression of the genotype
What is codominance
Both alleles contribute to the phenotype
What can a change in DNA do
Affect the phenotype by altering the sequence of amino acids in a protein
What are monohybrid crosses
Genetic crosses of single gene combinations
