Genetics exam 1

Question 1

Histones

Answer 1

DNA packaging is achieved by the association of DNA with a set of proteins

Question 2

Heterochromatin

Answer 2

• Very compact and dense DNA
• mostly formed by regions of genome with no genes or genes that are permanently repressed
• Most of Y chromosome is in heterochromatin.
• Centromeres and telomeres do not have genes on them and they are made of heterochromatin

Question 3

Euchromatin

Answer 3

• Chromatin is more relaxed
• Allow genes to be turned on and OFF

Question 4

chromatin

Answer 4

chromosomes are in a ‘relaxed state’

Question 5

Kinetochores

Answer 5

are made of protein and they bind both the centromere and the spindle fibers

Question 6

CENP-A, a centromere-specific Histone

Answer 6

is only present at the centromeres, it helps kinetochores attached at the right place

Question 7

DNA replication

Answer 7

1. Before entering Mitosis, cells create a copy of its genome through a process called DNA replication
2. This process occurs in S-phase and ensures the formation of two cells with identical genetic material after Mitosis.

Question 8

DNA replication is semiconservative

Answer 8

• Helix unwound and ‘new’ strands are formed using the ‘old’ as template.
• The final result are two new helices containing one ‘old’ strand and one ‘new’ strand.

Question 9

origins of replication

Answer 9

DNA replication start at the so-called origins of replication, an specific DNA sequence that recruits several components required to initiate transcription

Question 10

DNA polymerases

Answer 10

• The enzyme that actually do the synthesis of DNA during DNA replication by adding nucleotides
• They catalyze chain elongation: the addition of new nucleotides to a replicating strand.
• They need a primer to start DNA synthesis and a template to make a faithful copy. Primer can be DNA or RNA

Question 11

exonuclease

Answer 11

activity allow DNA polymerase to chew back the newly synthesized strand and correct the error.

Question 12

Nucleoside

Answer 12

SUGAR + NITROGENOUS BASE

Question 13

Nucleotide

Answer 13

NUCLEOSIDE + PHOSPHATE GROUP(S)

Question 14

Nucleic Acids

Answer 14

STRING OF NUCLEOTIDES BOUND BY PHOSPHODIESTER BONDS

Question 15

Nucleic acids (Primary structure)

Answer 15

sequence of nucleotides bound by phosphodiester bonds

Question 16

Nucleic acids (Secondary structure)

Answer 16

determined by interactions between nitrogenous bases

Question 17

In humans we found three major RNA TYPES:

Answer 17

• Messenger RNA (mRNA)
• Transfer RNA (tRNA)
• Ribosomal RNA (rRNA)

Question 18

Messenger (mRNA)

Answer 18

• Formed during gene transcription
• Serves as a template for protein synthesis
• In essence, mRNA is the link between DNA information (in the genome, nucleus) and Protein production (in the cytoplasm

Question 19

Transfer (tRNA)

Answer 19

• Translate nucleotide sequence into protein sequence
• they are the key for the ‘genetic code’ as they Match codons with aminoacids.

Question 20

Ribosomal (rRNA)

Answer 20

• Ribosomes are formed by a mix of proteins (~35%) and RNA (65%)
• There are two subunits, large and small, that serve as docking place for mRNA, tRNA and the nascent Protein.

Question 21

Major features of primary structure

Answer 21

• Two long chains Chains (Double stranded)
• Chains are antiparallel: they run in opposite directions
• The two strands are hold together through the pairing of nitrogenous bases of opposite strands as a result of hydrogen bonds between A and T (2 hydrogen bonds) and C and G (3 hydrogen bonds)
• The two strands are called to be complementary

Question 22

Major features of secondary structure

Answer 22

• The two chains are coiled around a central axis, forming a right-handed double helix
• The nitrogenous bases are flat structures, lying perpendicular to the axis; they are ‘stacked’ on one another; located inside the structure

Question 23

TELOMERES

Answer 23

• The natural ends of chromosomes
• Composed of a highly repetitive sequence
• MAIN FUNCTION OF TELOMERES IS PROTECTION

Question 24

Telomere replication problem

Answer 24

Telomeres get shorter every cell cycle. Telomeres shortening leads to unprotected ends. Short Telomeres plays a central role in the development of age-related diseases.

Question 25

Telomerase

Answer 25

Can extend telomere ends

Question 26

Chromosomal satellite

Answer 26

part of the end of a chromosome that is separated from the rest of the chromosome by a secondary constriction

Question 27

Transposons (jumping genes)

Answer 27

are DNA sequences that can insert themselves in other parts of the genome (i.e. the name jumping genes!)

Question 28

two types of Transposons

Answer 28

Retrotransposons: require reverse transcriptase to “jump” from one site of the genome to another. The reverse transcriptase is encoded in the transposon
DNA Transposons: that do not require reverse transcriptase, but “jump” as DNA thanks to a transposase enzyme encoded in the transposon

Question 29

DNA is Semiconservative

Answer 29

the produce results in one old and new strand

Question 30

DNA is Semi-discontinuous

Answer 30

there is a leading strand and lagging strand

Question 31

DNA is bidirectional

Answer 31

it replicates both way

Question 32

DNA is concurrent

Answer 32

replication is occurring at the same time, same rate, in the same directional.

Question 33

Helicase

Answer 33

Unwinds DNA

Question 34

Primase

Answer 34

enzyme that places primers

Question 35

ligase

Answer 35

“glues”/ connect Okazaki fragments

Question 36

Topoisomerase

Answer 36

It on either ends of helicase and relieves tension as DNA unwinds