DNA
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114 Terms
What does DNA stand for?
Deoxyribonucleic acid.
What is DNA made of?
Two chains of connected nucleotides.
What are the three components of a nucleotide?
Phosphate group, deoxyribose sugar, and a nitrogenous base.
What type of bond joins the sugar and phosphate in DNA?
Covalent bonds.
What type of bond joins complementary nitrogenous bases?
Hydrogen bonds.
What shape does DNA form?
Double helix.
What are histones?
Eight proteins that DNA wraps around.
What is a nucleosome?
DNA wrapped around eight histone proteins.
Which bases are purines?
Adenine (A) and Guanine (G).
Which bases are pyrimidines?
Thymine (T) and Cytosine (C).
Which bases pair together?
A-T and G-C.
Why must a purine pair with a pyrimidine?
To maintain the constant width of the DNA double helix.
What is a codon?
Three nucleotides that code for one amino acid.
What is a gene?
A sequence of codons that codes for a specific protein.
What is chromatin?
Long DNA strands loosely coiled when the cell is not dividing.
What is a chromosome?
Highly condensed DNA visible during cell division.
How many chromosomes do humans have?
46 (23 pairs).
When is chromatin found?
When the cell is not dividing.
When are chromosomes found?
During cell division.
Which can be seen under a light microscope?
Chromosomes.
What is the structure of nuclear DNA?
Double-stranded and linear.
What is the structure of mitochondrial DNA?
Double-stranded and circular.
Which DNA wraps around histones?
Nuclear DNA.
Which DNA is inherited from both parents?
Nuclear DNA.
Which DNA is inherited only from the biological mother?
Mitochondrial DNA.
Where is nuclear DNA located?
Nucleus.
Where is mitochondrial DNA located?
Mitochondria.
What is DNA replication?
The semi-conservative process of producing an identical copy of DNA.
Why is replication called semi-conservative?
Each new DNA molecule contains one original strand and one new strand.
What enzyme unzips DNA?
Helicase.
What bonds does helicase break?
Hydrogen bonds.
What is a template strand?
The original DNA strand used to build a complementary strand.
What enzyme adds complementary DNA nucleotides?
DNA polymerase.
What enzyme lays RNA primers?
Primase.
Which direction does primase read DNA?
3' → 5'.
Which direction does DNA polymerase synthesize DNA?
5' → 3'.
What is the leading strand?
The strand synthesized continuously.
What is the lagging strand?
The strand synthesized in Okazaki fragments.
What joins Okazaki fragments together?
DNA ligase.
How many pairs of chromosomes do humans have?
23 pairs.
How many are autosomes?
22 pairs.
How many are sex chromosomes?
1 pair.
What are alleles?
Alternative forms of the same gene.
How many chromosomes does each parent contribute?
One chromosome from each pair.
Is Huntington's disease dominant or recessive?
Dominant autosomal.
Is PKU dominant or recessive?
Autosomal recessive.
Is haemophilia dominant or recessive?
Sex-linked recessive.
Is colour blindness dominant or recessive?
Sex-linked recessive.
What mnemonic remembers these conditions?
"HuDA hit a PAR on a HaRSh CouRSe."
What is co-dominance?
Two alleles are equally dominant and both are expressed.
How are co-dominant alleles written?
Capital letters with subscripts (e.g. B¹ and B²).
What suggests an autosomal condition?
Males and females are affected equally.
What suggests a sex-linked recessive condition?
More males than females are affected.
If a female has a sex-linked recessive disorder, what is true of her sons?
All will be affected.
If both parents have a sex-linked recessive disorder, what is true of their daughters?
All daughters will be affected.
What indicates a dominant pedigree?
Every affected child has an affected parent and the trait does not skip generations.
What indicates a recessive pedigree?
The trait can skip generations and affected children may have unaffected parents.
What are the two stages of protein synthesis?
Transcription and translation.
Where does transcription occur?
Nucleus.
Where does translation occur?
Ribosomes.
Why can't DNA leave the nucleus?
It is too large.
What does DNA provide?
Instructions for making proteins.
Give four examples of proteins.
Enzymes, antibodies, hormones, haemoglobin.
What is a DNA triplet?
Three DNA bases coding for one amino acid.
What is an mRNA codon?
Three RNA bases coding for one amino acid.
What is transcription?
Copying DNA into mRNA.
What enzyme performs transcription?
RNA polymerase.
What starts transcription?
Chemical messengers bind to the promoter region.
Which DNA strand does RNA polymerase read?
Template strand.
Which direction does RNA polymerase read DNA?
3' → 5'.
Which direction is mRNA synthesized?
5' → 3'.
Which DNA strand matches mRNA?
Coding strand (except U replaces T).
What base replaces thymine in RNA?
Uracil.
What happens at the termination sequence?
RNA polymerase stops and releases mRNA.
How does mRNA leave the nucleus?
Through nuclear pores.
Is DNA single or double stranded?
Double stranded.
Is RNA single or double stranded?
Single stranded.
Which sugar is in DNA?
Deoxyribose.
Which sugar is in RNA?
Ribose.
Which base pairs with adenine in DNA?
Thymine.
Which base pairs with adenine in RNA?
Uracil.
What is translation?
Producing a protein using information in mRNA.
What are proteins made of?
Amino acids.
What determines a protein's function?
The order of amino acids.
What is a codon?
Three bases on mRNA.
What is an anticodon?
Three complementary bases on tRNA.
What is the role of tRNA?
Carry the correct amino acid to the ribosome.
What does the codon code for?
An amino acid.
What is the start codon?
AUG.
What amino acid does AUG code for?
Methionine.
What does UAG code for?
Stop.
What amino acid does CCU code for?
Proline.
What amino acid does CUC code for?
Leucine.
Where does translation begin?
At the AUG start codon.
Which direction does the ribosome read mRNA?
5' → 3'.
What bonds join amino acids?
Peptide bonds.
Does peptide bond formation require energy?
Yes.
What happens after tRNA delivers its amino acid?
It detaches and can collect another amino acid.
What happens when a stop codon is reached?
The polypeptide chain is released.
What is a polypeptide?
A chain of amino acids that forms a protein.