Nucleic Acids - B7 Flashcards
How many chromosomes do humans have?
46 - 23 pairs
Why is DNA a polynucleotide?
It is made up of lots of nucleotides
What molecules make up a nucleotide?
Phosphate, deoxyribose sugar, a nitrogenous base
What type of sugar is a deoxyribose sugar?
A pentose sugar
What is the bond between the phosphate molecule and the deoxyribose sugar and how is it formed?
A phosphodiester bond, formed by condensation
What is the bond between a deoxyribose sugar and the nitrogenous base and how is it formed?
A glycosidic bond, formed by condensation
What are the four types of nitrogenous base in DNA? What are the pairs?
Adenine - Thymine
Cytosine - Guanine
What makes the base pairs complimentary?
They have a specific no. of bonds.
What type of bond is between the base pairs?
Hydrogen bonds
They are weak alone, but when there are lots together, they are strong.
How many Hydrogen bonds are between each of the base pairs?
A+T -> 2 bonds
C+G -> 3 bonds
What does it mean if DNA is anti-parrallel?
one strand goes up and one strand goes down
Why is DNA important?
It contains information of how to make polypeptide proteins. These proteins then regulate cell metabolism and behaviour
What is the name for 3 bases placed together?
A codon - 1 amino acid
What is a genome?
All of the genes in an organism
Why is the genetic code known as universal?
The same 3 bases code for the same amino acids in every living thing.
What determines an organisms characteristics?
The sequence of bases and quantity of DNA that determines the organisms characteristics.
What are the different structural components in a DNA molecule?
-sugar-phosphate backbone
-long-large molecule
-(double)helix/ coiled
-double stranded
-weak hydrogen bonds in small no.s
-base sequence
What is the function of the DNA structure phosophate-sugar backbone?
strength - protects bases
What is the function of DNA being a large/long molecule?
stores more genetic information
What is the function of the DNA structure being coiled/a double helix?
it is compact
What is the function of DNA being double stranded?
there is 1 template strand
-used in DNA replication and transcription
-if damaged or things go wrong, there is a back up
What is the function of DNA having weak hydrogen bonds in small no.s?
the bonds can be broken easily for DNA replication
What is the function of base sequences in DNA?
it is the genetic information - proteins from transcription
What is Chargaff’s Rule?
There will be:
-equal amounts if adenine and thymine
-equal amounts of cytosine and guanine
If we know the no. of adenine on one strand, we know the no. of thymine on the other strand.
What is a purine and what does it pair with?
A purine(with 2 rings) always pairs with a pyrimidine(1 ring)
Which bases are purines?
adenine and guanine
Which bases are pyrimidines?
cytosine and thymine
What is a proteome?
The particular range of proteins that a cell makes
What are the 3 types of RNA?
-Messenger RNA (mRNA)
-Transfer RNA (tRNA)
-Ribosomal RNA (rRNA)
What are the differences between DNA and RNA?
-RNA is single stranded(no base pairs)
-RNA has uracil instead of thymine
-RNA=ribose sugar, DNA=deoxyribose sugar
-RNA is shorter
Is mRNA single stranded?
yes
Why is mRNA shorter than DNA?
it is a copy of a single gene
What are the sequences of bases on mRNA complementary to?
The sequence of bases it’s copying
What are the differences between tRNA and mRNA?
-they’re both single stranded(similarity)
-different shapes: mRNA is linear, tRNA is a clover-leaf shape
-tRNA is much shorter (around 70 bases, when it is usually 100s for RNA)
-tRNA has hydrogen bonds between bases
-tRNA has complementary base pairs
What are two structural features of tRNA?
-The anticodon(the codon is very specific and only has three specific bases)
-The amino acid attachment site(there is a specific amino acid which tRNA carries)
Which pentose sugar is in:
a)DNA
b)mRNA
c)tRNA
a)deoxyribose
b)ribose
c)ribose
What purine bases are in:
a)DNA
b)mRNA
c)tRNA
adenine and guanine for all
What pyrimidine bases are in:
a)DNA
b)mRNA
c)tRNA
a)cytosine and thymine
b)cytosine and uracil
c)cytosine and uracil
How many polynucleotide strands are in:
a)DNA
b)mRNA
c)tRNA
a)2
b)1
b)1
Is hydrogen bonding absent or present in:
a)DNA
b)mRNA
c)tRNA
a)present- holds 2 anti-parallel strands together -> A-T G-C
b)absent
c)present - H bonds form a clover-leaf shape
What is the number of nucleotides in these chains:
a)DNA
b)mRNA
c)tRNA
a)many millions
b)severel 100s-1000s
c)about 75
What are ribosomes the site of?
Ribosomes are the site of proteinsynthesis and is also where translation happens
What are the two structures that ribosomes are made from?
rRNA and proteins
What are the two subunits which ribosomes are made from?
There is a large and small subunits where rRNA is found
What does the small subunit of a ribosome do?
The small subunit reads code on mRNA
What does the large subunit of a ribosome molecule do?
The large subunit adds amino acid ->contains enzymes for polypeptide reactions
What does rRNA help to do?
rRNA helps to read the genetic code
Why do chloroplasts and mitochondria have circular DNA?
Chloroplasts and mitochondria used to be their own organisms(prokaryotes) s now have circular DNA of their own. This DNA is shorter with fewer genes, but still present.
What is the difference between normal DNA and the DNA found in chloroplasts and mitochondria?
-circular, not linear
-shorter than DNA…
-…so has less genes
-introns absent(bacteria don’t have this, and they used to be prokaryotes)
-no histones
These are also features found in prokaryotes ->chloroplasts used to be prokaryotes
What does ATP have a similar structure to?
ATP has a similar structure to RNA - has two more phosphate groups.
What does ATP consist of?
ATP is a molecule of ribosome and adenine(together known as adenosine) and three phosphate groups
What reaction is used to go from ATP to ADP?
hydrolysis
-releases energy
-uses the enzyme ATP hydrolase
-add water -> to hydrolyse and break the bond
-one phosphate is released ->energy
What reaction is used to go from ADP to ATP?
condensation
-energy used
-uses enzyme ATP synthase
-H20 released
-requires some energy, but less than what was released
What is phosphorylation?
The phosphate group is often transferred to other molecules to lower their activation energy and make them more reactive
What is a chromosome?
tightly wound DNA
What do the DNA strands wrap around in a chromosome?
DNA strands wrap around histones(which are proteins present in all except mitochondria and chloroplasts) and are tightly wound to a long coil
What is DNA in chromosomes held in place by?
DNA in chromosomes is held in place by proteins
What are DNA + histones known as?
chromatin fibre
What are homolagous pairs?
There is one gene from each parent in each chromosome pair
-equivalent genes from mother and father
-carry the same genes in the same positions
-they’re the same shape
What is a karyotype?
all a person’s chromosomes on display(the diploid no. of chromosomes)
What is the locus?
The location of a gene is known as the locus(loci -plural)
-the same for everyone
What is the centromere?
protein found in the middle of a chromosome
What determines the order of amino acids?
the base sequence on the gene
What is the definition of a gene?
a gene is a section of DNA that codes for a particular polypeptide/protein and codes for functional RNA
What are introns?
non-coding DNA found in genes(only in genes)
What are exons?
DNA which codes for proteins
True or false: prokaryotic DNA contains introns
false - prokaryotic DNA doesn’t contain introns
What are non-coding repeats?
non-coding DNA BETWEEN genes
-each region contains a sequence of bases, repeated a no. of times
-no. of repeats varies from person to person
-these are used in genetic fingerprinting
What is an allele?
different forms of the same gene
