Genes and Inheritance Flashcards
Genome Definition:
All of the DNA found in an organism
Gene Definition:
A section of a molecule of DNA that codes for a specific protein
Where are genes located
On chromosomes in the nucleus
DNA structure
Double helix (2 strands)
Bases paired up (complementary base pairing) A-T, C-G
RNA structure
Single strand
A-U, C-G
Nucleotide made up of:
Phosphate
Sugar (Ribose/Deoxyribose)
Nitrogenous Base
5 types of bases
Adenine
Thymine (DNA)
Cytosine
Guanine
Uracil (RNA)
Codon/Anticodon
Triplet of (unpaired) bases
Transcription (nucleus)
Occurs in Nucleus
-Part of DNA unwinds, bonds between base pairs break
-Template strand exposed: ONLY ONE STRAND
-Free mRNA nucleotides in nucleus bind to complementary nucleotides
-mRNA nucleotides join together, forming mRNA strand
-mRNA leaves the nucleus via nuclear pore
-mRNA complementary copy of DNA code from original gene
Translation (cytoplasm)
Occurs in ribosomes
-mRNA attaches to ribosome
-Free tRNA molecules in cytoplasm have anticodons on one end, amino acid on the other
! - each specific anticodon corresponds to a specific amino acid
-The anticodon (tRNA) pairs to its complementary codon (mRNA)
-This repeats and peptide bonds are formed between AAs
-This continues until a ‘stop’ codon is reached on mRNA
-Amino acid chain folds to form protein
Why is RNA needed
DNA cannot leave the nucleus as it is a big molecule
Alleles Definition:
Variations of the same gene
e.g. blue/black eyes
Dominant Allele (A):
Allele that is always expressed
Recessive Allele (a):
Allele that is expressed only when there is no dominant allele
Homozygous and Heterozygous:
Both alleles are the same vs
Both alleles are different
Genotype and Phenotype
G: Alleles for a particular characteristic
Ph: Physical appearance caused by alleles
Co-dominance
When neither allele is dominant, both are expressed in phenotype
Polygenic Inheritance definition:
When 2 or more genes work together to control a characteristic
Male Female genotype
XY, XX
Diploid Definition
Cell containing 2 sets of chromosomes
Mitosis (IPMAT)
-Produces diploid cells, identical to parent cell
Interphase: DNA in chromosomes replicate themselves for mitosis
Prophase: Chromatids condense and become visible, and nuclear membrane disappears
Metaphase: Spindle forms, chromatids line up in middle
Spindle attaches to their centromeres
Anaphase: Spindle fibres shorten and pull chromatids to poles, separating them
Telophase: New membrane form around chromosomes at each end of cells, forming 2 new nuclei. Cytoplasm divides to form 2 daughter cells that are diploid
Meiosis
-Produces 4 genetically different haploid cells
Cells divide twice (IPMAT x 2)
Metaphase 1: Maternal and Paternal Chromosomes pair up along center but are not separated
Metaphase 2: Same as mitosis, seperated
All daughter cells are haploid
Homologous Chromosome Definition:
Matching (but unidentical) pairs of a chromosome
Mitosis vs Meiosis
2 cells prod. vs 4 cells prod.
diploid vs haploid
genetically identical vs different
Mutation definition:
A random process in genes or chromosomes that changes a DNA sequence
Insertion:
Extra nucleotide added
Frameshift mutation - whole amino acid sequence from this point onwards changes as each triple after is now different (every codon shifts)
Deletion
Nucleotide deleted
Frameshift mutation - whole amino acid sequence from this point onwards changes
Substitution
Different nucleotide used
Triplet of bases in which mutation occurs changes
Rest of the chain unaffected
! - new triplet could still code for same amino acid (AAs have more than one code)
Inversion
Order of bases in a triplet is reversed e.g CCT -> TCC
Similar effects to substitution
How can mutations be passed on to offspring?
Mutation in gametes
Increases in risk of mutation
Mutagens:
Ionising radiation - Gamma, X-rays, UV
Chemicals in cigarettes, mustard gas, nitrous oxide, benzenes
