Chapter 3- Genes

Question 1

How many DNA molecules in a cell?

Answer 1

46 in q human cell- but there are thousands of genes

Question 2

Where are genes located?

Answer 2

A gene occupies a specific position on one type of chromosomes where this located this position is called the locus of a gene

Question 3

Who is Gregor Mendel and what did he do?

Answer 3

He crossed varieties of pea plants and deduced that the differences between the varieties that he crossed together were due to heritable factors

Question 4

What are alleles?

Answer 4

Various specific forms of gene

Question 5

Alleles are alternative forms of the same gene there for what what do they have the same of?

Answer 5

The same locus- occupy the same position on one type of chromosomes

Question 6

How do alleles differ from each other?

Answer 6

Differ from each other by one or a few bases

Question 7

What’s a single nucleotide polymorphism (SNPs)?

Answer 7

Position in a gene where more than one base may be present

Question 8

How are new alleles formed?

Answer 8

By gene mutation

Question 9

What type of mutation can occur to change an allele?

Answer 9

A base substitution - one base is replaced by a different base

Question 10

What can some mutations do?

Answer 10

Mutations that develop into gametes can be passed on to offspring and cause genetic disease

Question 11

What is a genome?

Answer 11

The genome is the whole of the genetic information of an organism

Question 12

In humans what is it that the genome consists of?

Answer 12

46 molecules that form the chromosomes in the nucleus plus the DNA molecules in the mitochondrion

Question 13

What is the human genome project?

Answer 13

The entire base sequence of human genes

Question 14

What is a gene?

Answer 14

Is a heritable factor that consists of a length of DNA and influences a specific characteristic

Question 15

Definition of a gene mutation

Answer 15

It is a change in the nucleotide sequence of a section of DNA coding for particular feature

Question 15

What is the cause of sickle-cell anaemia?

Answer 15

Base substitution mutation

Question 16

What does base substitution result in?

Answer 16

A change in a single messenger RNA codon during transcription

Question 17

In sickle-cell anaemia what is the code on the exchange to result in a disease?

Answer 17

The 6th codon for the beta chain of haemoglobin is changes from GAG to GTG

Question 18

The change of GAG to GTG does what?

Answer 18

Causes a change in mRNA codon (GAG to GTG) resulting in a single amino acid change of glu to val

Question 19

What does DNA change due? What does messenger rna change to? What does it amino acid change to?

Answer 19

DNA = GAG to GTG
mRNA = GAG to GUG
Amino acid = glu to val

Question 20

What does the amino acid alter?

Answer 20

Alters shape of haemoglobin - forms fibrous insoluble strands- red blood cells adopt a sickle cell shape

Question 21

What are three bad consequences of sickle-cell Amenia?

Answer 21

1) insertable haemoglobin can’t effectively carry oxygen which means they can be weakness, shortness of breath, tiredness
2) sickle-cell may accumulate in the capillaries and form clots, blocking blood supply to vital organs and causing health problems
3) cause anaemia (low RBC) as cells are destroyed more rapidly than normal RBC

Question 22

Who’d of sickle-cell Amenia occur in? What is one benefit?

Answer 22

It occurs in individuals who have 2 copies of the co-dominant sickle cell allele
Heterozygous carriers have increased resistance to malaria without the disease of sickle cell