Genes and Inheritance

Question 1

Genome Definition:

Answer 1

All of the DNA found in an organism

Question 2

Gene Definition:

Answer 2

A section of a molecule of DNA that codes for a specific protein

Question 3

Where are genes located

Answer 3

On chromosomes in the nucleus

Question 4

DNA structure

Answer 4

Double helix (2 strands)
Bases paired up (complementary base pairing) A-T, C-G

Question 5

RNA structure

Answer 5

Single strand
A-U, C-G

Question 6

Nucleotide made up of:

Answer 6

Phosphate
Sugar (Ribose/Deoxyribose)
Nitrogenous Base

Question 7

5 types of bases

Answer 7

Adenine
Thymine (DNA)
Cytosine
Guanine
Uracil (RNA)

Question 8

Codon/Anticodon

Answer 8

Triplet of (unpaired) bases

Question 9

Transcription (nucleus)

Answer 9

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

Question 10

Translation (cytoplasm)

Answer 10

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

Question 11

Why is RNA needed

Answer 11

DNA cannot leave the nucleus as it is a big molecule

Question 12

Alleles Definition:

Answer 12

Variations of the same gene
e.g. blue/black eyes

Question 13

Dominant Allele (A):

Answer 13

Allele that is always expressed

Question 14

Recessive Allele (a):

Answer 14

Allele that is expressed only when there is no dominant allele

Question 15

Homozygous and Heterozygous:

Answer 15

Both alleles are the same vs
Both alleles are different

Question 16

Genotype and Phenotype

Answer 16

G: Alleles for a particular characteristic
Ph: Physical appearance caused by alleles

Question 17

Co-dominance

Answer 17

When neither allele is dominant, both are expressed in phenotype

Question 18

Polygenic Inheritance definition:

Answer 18

When 2 or more genes work together to control a characteristic

Question 19

Male Female genotype

Answer 19

XY, XX

Question 20

Diploid Definition

Answer 20

Cell containing 2 sets of chromosomes

Question 21

Mitosis (IPMAT)

Answer 21

-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

Question 22

Meiosis

Answer 22

-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

Question 23

Homologous Chromosome Definition:

Answer 23

Matching (but unidentical) pairs of a chromosome

Question 24

Mitosis vs Meiosis

Answer 24

2 cells prod. vs 4 cells prod.
diploid vs haploid
genetically identical vs different

Question 25

Mutation definition:

Answer 25

A random process in genes or chromosomes that changes a DNA sequence

Question 26

Insertion:

Answer 26

Extra nucleotide added
Frameshift mutation - whole amino acid sequence from this point onwards changes as each triple after is now different (every codon shifts)

Question 27

Deletion

Answer 27

Nucleotide deleted
Frameshift mutation - whole amino acid sequence from this point onwards changes

Question 28

Substitution

Answer 28

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)

Question 29

Inversion

Answer 29

Order of bases in a triplet is reversed e.g CCT -> TCC
Similar effects to substitution

Question 30

How can mutations be passed on to offspring?

Answer 30

Mutation in gametes

Question 31

Increases in risk of mutation

Answer 31

Mutagens:
Ionising radiation - Gamma, X-rays, UV
Chemicals in cigarettes, mustard gas, nitrous oxide, benzenes