Lecture 4

Question 1

define gene

Answer 1

unit of heredity that comprises a stretch of DNA that codes for a type of protein- some visible, some not visible

Question 2

define autosomes

Answer 2

The first 22 pairs of chromosomes other than the sex chromosome

Question 3

What is the 23rd pair of chromosomes called?

Answer 3

sex chromosomes

Question 4

How is a karyotype produced?

Answer 4

produced by staining and photographing the chromosomes as they divide- individual chromosomes are then cut out and paired with their homologous pair

Question 5

how do biologists identify the homologous pairs?

Answer 5

based on size, shape, position of centromere and stained bands

Question 6

define loci

Answer 6

location of the allele on the chromosome

Question 7

how many chromosomes do sex cells such as sperm or eggs have?

Answer 7

23 haploid chromosomes

Question 8

define gene mapping

Answer 8

the process of determining the locus for a particular biological trait

Question 9

locus for a gene written as 11q1.4 means what?

Answer 9

q arm of 11th chromosome, band 1, sub band 4

Question 10

the tallest chromosome (#1) has how many genes?

Answer 10

4200 genes

Question 11

Shortest y chromosome has how many chromosomes?

Answer 11

450 genes

Question 12

What are genetic disorders caused by?

Answer 12

mutation of genes

Question 13

Disorders caused by mutation of genes is called what?

Answer 13

muted/defective/disease genes

Question 14

define mutation

Answer 14

a random, undirected, heritable variation caused by alteration in the gene nucleotide sequence at some point of DNA of the cell

Question 15

How can mutation happen?

Answer 15

addition, deletion, substitution

Question 16

What happens in substitution?

Answer 16

One base pair is inserted in place of another- takes place at time of DNA replication due to error of DNA polymerase

Question 17

Missense mutation

Answer 17

When the substitution results in a codon that simply causes a different amino acid production

Question 18

nonsense mutation

Answer 18

If it stops protein synthesis by becoming a stop codon sooner than predicted

Question 19

Frame shift mutation

Answer 19

Occurs when one or two base pairs inserted/deleted- wrong aa are produced down stream

Question 20

Point mutation

Answer 20

any insertion/deletion entirely

Question 21

Chromosomal abberations

Answer 21

Any change in the normal structure of a chromosome-Whole chromosome extra, missing or both

Question 22

What happens in a tri-nucleotide repeat disorders

Answer 22

gene is extended in length

Question 23

How can mutations be induced?

Answer 23

by UV rays, alkylating agents, 5 Bromouracid, Acridin dyes

Question 24

How many amino acids are there?

Answer 24

20 aa

Question 25

What pedigree pattern is shown from autosomal dominant disease?

Answer 25

vertical pattern of inheritance

Question 26

Complete Penetrance

Answer 26

Means that all individuals who have defective allele show clinical symptoms of the disease

Question 27

Reduced Penetrance

Answer 27

(incomplete penetrance)- when some individuals fail to express the trait, even though they carry the defective allele

Question 28

What pedigree pattern is shown from autosomal recessive disease?

Answer 28

horizontal pedigree pattern

Question 29

examples of autosomal recessive disorders

Answer 29

cystic fibrosis, sicke cell, tay-sachs, phenylketonuria and galactosemia

Question 30

Define incomplete dominance

Answer 30

alleles are neither dominant nor recessive- when two different alleles are combined, the resulting expression is somewhere between the two

Question 31

example of incomplete dominance

Answer 31

snapdragon flower color- crossing homozygous red with homozygous white snapdragon plants produces heterozygous offspring that have pink flowers

Question 32

example of incomplete dominance in humans

Answer 32

inheriting a gene for curly hair from one parent and a gene for straight hair from the other will give wavy hair

Question 33

Define single dominance

Answer 33

either we have the allele or we don't

Question 34

examples of single dominance

Answer 34

ear attachment, tongue rolling, PTC tasting

Question 35

define co-dominance

Answer 35

The gene present in both alleles expresses the trait in phenotype

Question 36

Example of human co-dominance disorder

Answer 36

ABO blood type (AB blood group is A and B blood)

Question 37

Define polygenic inheritance

Answer 37

several genes for one trait - multiple alleles for one trait

Question 38

What blood type has an absence of antigens?

Answer 38

Blood type O

Question 39

define multiple alleles

Answer 39

having more than two different alleles for the gene