4) Genetic Information, Variation, and Relationships Between Organisms

Question 1

in terms of their purpose, what is the difference between RNA and DNA?

Answer 1

DNA holds genetic information, whereas RNA transfers genetic information from DNA to ribosomes

Question 2

what are ribosomes made of?

Answer 2

rRNA and proteins

Question 3

what are the components of DNA nucleotide?

Answer 3

deoxyribose
a phosphate group
an organic base

Question 4

which bases are purine bases? why?

Answer 4

adenine and guanine
they have double ring structures

Question 5

what are the components of an RNA nucleotide?

Answer 5

ribose
a phosphate group
an organic base

Question 6

which organic bases are pyrimidines? why?

Answer 6

thymine, uracil, and cytosine
they have single ring structure

Question 7

which of the bases can a DNA nucleotide have?

Answer 7

adenine, thymine, cytosine, guanine

Question 8

which of the bases can an RNA nucleotide have?

Answer 8

adenine, uracil, cytosine, guanine

Question 9

how are nucleotides joined? give the bond and reaction

Answer 9

by phosphodiester bonds formed in condensation reactions

Question 10

what bonds join complementary bases?

Answer 10

hydrogen bonds

Question 11

what is the genetic code?

Answer 11

the order of bases on DNA, which consists of triplets of bases

Question 12

what is a codon?

Answer 12

a sequence of 3 bases on mRNA that codes for a specific amino acid

Question 13

what is a gene?

Answer 13

a length of DNA on a chromosome that codes for a sequence of amino acids in a polypeptide chain

Question 14

what is a locus?

Answer 14

the location of a gene on a chromosome

Question 15

what are introns and exons?

Answer 15

• introns are non-coding sections of DNA
• exons are coding sections

Question 16

how many different amino acids are there?

Answer 16

20

Question 17

how many possible triplets are there?

Answer 17

64

Question 18

what does non-overlapping mean?

Answer 18

each base in a sequence is read once and is only part of one triplet

Question 19

what does degenerate mean, in relation to the genetic code?

Answer 19

more than one triplet codes for the same amino acid

Question 20

what is the advantage of the genetic code being degenerate?

Answer 20

reduces the number of mutations

Question 21

what are the differences between eukaryotic DNA and prokaryotic DNA?

Answer 21

EUKARYOTIC
- long and linear
- associated with histones

PROKARYOTIC
- short and circular
- not associated with proteins

Question 22

how many chromosomes are there in each human body cell?

Answer 22

46

Question 23

how are chromosomes arranged in each cell?

Answer 23

in homologous pairs

Question 24

what is a homologous pair?

Answer 24

two chromosomes that carry the same genes at the same locus

Question 25

why are the chromosomes in a homologous pair not identical?

Answer 25

because they can carry different alleles of the same gene

Question 26

which chromosome determines sex?

Answer 26

23

Question 27

what is an allele?

Answer 27

an alternative version of the same gene

Question 28

what are the two stages of protein synthesis?

Answer 28

transcription and translation

Question 29

what is transcription?

Answer 29

the formation of pre-mRNA in eukaryotes and mRNA in prokaryotes from a section of the template strand of DNA

Question 30

where does transcription occur?

Answer 30

in the nucleus

Question 31

during what process is mRNA made?

Answer 31

transcription

Question 32

what is the role of mRNA?

Answer 32

carries the genetic code from the DNA to the ribosomes, where it's used to make a protein

Question 33

describe the structure of mRNA

Answer 33

single polynucleotide strand

Question 34

what are groups of 3 adjacent bases called in mRNA?

Answer 34

codons

Question 35

what process is tRNA involved in?

Answer 35

translation

Question 36

what is the role of tRNA?

Answer 36

carries the amino acids, used to make proteins, to the ribosomes

Question 37

describe the structure of tRNA

Answer 37

single polynucleotide strand folded into a clover shape

Question 38

what bonds hold tRNA into its clover shape?

Answer 38

hydrogen bonds between specific base pairs

Question 39

what do tRNA molecules have at each end?

Answer 39

an anticodon and an amino acid binding site

Question 40

what is an anticodon?

Answer 40

a sequence of 3 nucleotide bases at one end of a tRNA molecule that is specific to an mRNA codon

Question 41

where does transcription take place in eukaryotic and prokaryotic cells?

Answer 41

- eukaryotic = in the nucleus - prokaryotic = in the cytoplasm

Question 42

where does translation occur?

Answer 42

at the ribosomes in the cytoplasm

Question 43

describe the process of translation

Answer 43

- mRNA attaches to a ribosome and tRNA collects amino acids from cytoplasm and carries them to the ribosome - tRNA attaches to mRNA by complementary base pairing, two molecules of tRNA attach at a time - amino acids attached to two tRNA molecules join by a peptide bond and tRNA molecules detach from the amino acids to leave them behind - process repeats leading to the formation of a polypeptide chain until a stop codon is reached

Question 44

what is a genetic mutation?

Answer 44

any change in the base sequence or quantity of DNA

Question 45

what can a change in the base sequence of a gene result in?

Answer 45

a change to the sequence of amino acids

Question 46

why does a genetic mutation not always lead to a change in the amino acid sequence?

Answer 46

because the genetic code is degenerate (more than one triplet codes for the same amino acid)

Question 47

what are the types of genetic mutation?

Answer 47

- substitution - deletion - addition - inversion - duplication - translocation

Question 48

what are the two kinds of mutations that can occur in chromosomes?

Answer 48

polyploidy and non-disjunction

Question 49

what is polyploidy?

Answer 49

changes that occur in the whole set of chromosomes so that an individual has three or more sets of chromosomes instead of two

Question 50

what is non-disjunction?

Answer 50

when chromosomes fail to separate correctly in meiosis, resulting in the gametes and therefore any zygotes formed having one more or fewer chromosome than they should

Question 51

how many daughter cells are produced by meiosis?

Answer 51

4

Question 52

are daughter cells produced by meiosis genetically identical or unique?

Answer 52

genetically unique

Question 53

how many chromosomes do gametes have in relation to the parent cell?

Answer 53

half the number

Question 54

what is the role of meiosis?

Answer 54

production of haploid gametes

Question 55

why must gametes be haploid?

Answer 55

so that when two gametes fuse, the zygote produced is diploid

Question 56

by what two ways is genetic variation achieved?

Answer 56

- independent segregation - crossing over

Question 57

when does independent segregation occur?

Answer 57

during meiosis 1

Question 59

Describe the process of meiosis

Answer 59

1) DNA unravels and replicates so there are 2 copies of each chromosome 2) DNA condenses to form double-armed chromosomes each made from a sister chromatids 3) meiosis 1 - chromosomes arrange themselves into homologous pairs 4) Homologous pairs are separated, halving the chromosome number 5) meiosis 2 - each pair of sister chromatids, that make up each chromosome, are separated 6) 4 genetically different (from each other) haploid daughter cells are produced