3.1 Genes

Question 1

a gene is…

Answer 1

a heritable sequence of DNA that determines or influences a trait (physiological, physical, or behavioral)

Question 2

heritable…

Answer 2

can be passed down from parent to offspring

Question 3

locus

Answer 3

specific location on a chromosome where each gene is found
(when comparing 2 or more locations, refer to them as loci)

Question 4

genes have the ____________ both members of a ______________________.

Answer 4

same locus on, chromosome pair

Question 5

homologous chromosomes have…

Answer 5

the same genes located at the same loci

Question 6

Alleles are…

Answer 6

alternative forms of a gene that code for the different variations of a specific trait (ex. gene is eye color, alleles are brown and blue)

Question 7

since alleles are the alternative form of the one gene…

Answer 7

they have very similar gene sequences (only differ by one or a few bases), usually formed by mutation

Question 8

SNP (single nucleotide polymorphism)

Answer 8

• most common type of genetic variation in people
• when single base pair is replaced with another
• can lead to different alleles/versions of the gene

Question 9

mutation is…

Answer 9

any unpredictable and permanent change in nucleotide sequence of DNA in an organism- if mutation affects structure or characteristic of a protein, new allele may form

Question 10

most mutations occur in…

Answer 10

somatic (body cells) and are not passed on from one generation to the next, they are eliminated when the individual dies

Question 11

only mutations that occur in the formation of …

Answer 11

sperm and egg (gametes) can be inherited

Question 12

mutagens may…

Answer 12

interact with the DNA and prevent the correct base pairs from bonding during DNA replication

Question 13

beneficial mutations

Answer 13

change in gene sequence to create new allele/protein that is advantageous to survival and reproduction

Question 14

harmful mutation

Answer 14

change in the gene sequence to create a new allele/protein that is disadvantageous to survival and reproduction

Question 15

neutral mutation

Answer 15

change in the gene sequence does not affect survival and reproduction or does not change the allele/protein significantly

Question 16

missense mutation

Answer 16

change of amino acid (effect could vary)

Question 17

nonsense mutation

Answer 17

prematurely codes for a STOP codon (shortens protein chain)

Question 18

silent mutations

Answer 18

has no effect on amino acid sequence (recall: wobble hypothesis)

Question 19

point mutations

Answer 19

mutations arising from a change in a single nucleotide base

Question 20

frameshift mutations

Answer 20

mutations (usually insertions or deletions) that cause the reading frame to change (ie. triplet codons are changed)

Question 21

types of frameshift mutations

Answer 21

• insertion
• deletion
• 3 nucleotide insertion/deletion

Question 22

sickle cell anemia

Answer 22

occurs due to mutation on chromosome 11, in 6th codon of hemogoblin

Question 23

what does sickle cell trait do to hemoglobin

Answer 23

leads to production of valine (Hbs) instead of glutamine (Hba)

Question 24

effect of sickle cell trait on human health

Answer 24

production of abnormal RBCs with faulty hemoglobin gene
- causes Hb molecules to crystallize when oxygen levels in the blood are low
- as a result, RBCs sickle and get stuck in small blood vessels

Question 25

sickle cell relation to malaria

Answer 25

malaria invades RBCs and causes them to lyse
- people with sickle cell trait are resistant to malaria
- sickle cell anemia is more prevalent in areas where malaria is endemic (found)

Question 26

genome:

Answer 26

whole genetic information of an organism contained in the DNA

Question 27

genome in plants:

Answer 27

all DNA in chromosomes, nucleus, mitochondrion, chloroplast

Question 28

genome in prokaryotes:

Answer 28

much smaller, is the DNA in circular chromosome and in plasmids

Question 29

genome in humans:

Answer 29

consists of 46 nucleic acids that form the chromosomes in the nucleus and DNA in mitochondrion

Question 30

chromosomes in humans:

Answer 30

chromosome pairs 1-22 are autosomes
23rd pair are sex chromosomes (XX is female, XY is male)

Question 31

karyogram:

Answer 31

visual display of all chromosomes in a cell

Question 32

human genome project (HGP)

Answer 32

aimed to find the complete sequence of DNA bases in human genome

Question 33

finding of the HGP

Answer 33

• humans have 23,000 genes (less than expected)
• the majority of genome is not expressed, these are found to regulate gene expression
• many sections of DNA have regulatory functions
• genome sequence was from one individual so there might be minor differences between individuals

Question 34

why bother with HGP

Answer 34

could help with gene mapping, screening, medicine, ancestry

Question 35

genes of humans vs other organisms

Answer 35

bacteria< chicken< human < water flea < rice

Question 36

techniques for gene sequencing

Answer 36

• gel electrophoresis separates samples of DNA and creates bands that can be used for deduction
• coloured flurescent markers mark DNA copies and uses optical detector to deduce base sequence based on fluorescence colours