NUCLEIC ACID N CHROMOSOMES

Question 1

is RNA or DNA more stable?

Answer 1

• DNA is more stable as it is less reactive due to C-H bond at 2’ carbon
• RNA is less stable as it is more reactive due to O-H bond at 2’ carbon

Question 2

where is DNA found in eukaryotes and prokaryotes?

Answer 2

Eukaryotes : found in the nucleus

Prokaryote : circular, double-stranded DNA floats freely in the cytoplasm (nucleoid)

Question 3

what are purines and pyrimidines?

Answer 3

Purines : Adenine and Guanine (two rings)

Pyrimidine : Cytosine and Thymine (one ring)

Question 4

How are DNA nucleotides joined together?

Answer 4

Dehydration reaction which produces water and phosphodiester bond between two nucleotides

Question 5

What can genetic material do?

Answer 5

• must carry information ; genetic code
• must be able to replicate ; DNA replication
• must allow information change ; mutation
• govern the expression of the phenotype ; gene function

Question 6

How is DNA packaged?

Answer 6

DNA is wrapped tightly around histones and coiled tightly to form chromosomes

Question 7

What are histones?

Answer 7

a family of basic proteins that associate with DNA in the nucleus and help condense it into chromosome

Question 8

What are nucleosomes?

Answer 8

section of DNA wrapped around histone

Question 9

What are chromatin?

Answer 9

DNA and Histone proteins are collectively called chromatin

Question 10

Whats is DNA?

Answer 10

molecule that encodes the gentic information

Question 11

What are chromosomes made of?

Answer 11

• chromosomes are made up of many genes

- long strings of DNA wrapped tightly around histones which contributes to the threadlike structure

Question 12

What are autosomes?

Answer 12

chromosome 1-22 in humans which looks the same in both female and male

Question 13

What are sex chromosomes?

Answer 13

23rd pair of chromosomes which determines the gender

Question 14

what do female and male chromosomes look like?

Answer 14

female : XX (homogametic)

male : Xy (heterogametic)

Question 15

What is karyotyping?

Answer 15

a system to identify chromosomes by their size, shape and banding patterns produced by specific stains
- chromosomes are analysed by organising them into
karyotype

Question 16

What is Giemsa Staining?

Answer 16

staining chromosomes, specific for phosphate groups of DNA and attaches itself to regions of DNA where there are high amounts of A-T bonding

Question 17

what are alleles?

Answer 17

variant forms of a given gene

- each organism has a pair of allele for each trait ; 1 mother, 1 father

Question 18

What is homozygote?

Answer 18

HOMOZYGOUS : two identical alleles for a gene

Question 19

What is heterozygote?

Answer 19

HETEROZYGOUS : two different alleles for the same gene

Question 20

What does dominant allele do?

Answer 20

mask the expression of recessive allele

Question 21

What is genotype?

Answer 21

gentetic compostion of individual

Question 22

What is AA?

Answer 22

homozygous dominant genotype

Question 23

What is aa?

Answer 23

homozygous recessive genotype

Question 24

What is Aa?

Answer 24

heterozygous genotype

Question 25

What is phenotype?

Answer 25

characteristics that are the result of gene expression

Question 26

What is punnet square?

Answer 26

used to predict traits of an off-spring

Question 27

What is incomplete dominance?

Answer 27

appearance in a heterozygote of a trait that is an intermediate between either of the trait’s homozygous phenotypes

Question 28

What is co-dominance?

Answer 28

alleles of a gene pair are fully expressed resulting in an off-spring with a phenotype that is neither dominant nor recessive

Question 29

What are multiple alleles?

Answer 29

a series of 3 or more alternative alleles forms of a gene

e.g ABO blood type is controlled by a single gene (ABO gene)

Question 30

What is gene mutation?

Answer 30

permanent alteration in the DNA sequence that makes up a gene such that the sequence differs from what is found in most people
e.g sickle cell gene disorder

Question 31

What is cancer?

Answer 31

multifactorial and progressive genetic disorder

Question 32

what are chromsomal disorders?

Answer 32

Down syndrome (Trisomy 21)

• chromosome 21 does not separate correctly
• develop slower, heart & stomach illness and vary greatly in IQ