Genetic Information & Variation Flashcards
(28 cards)
What are the three components of nucleotides?
A pentose sugar, a phosphate group, an
Nitrogenous base.
Describe the structure of DNA.
Made up of a deoxyribose sugar, a
phosphate group, and one of four
organic bases (A,C,G,T). It is
double-stranded, and hydrogen bonds
between the bases form a helix shape
Describe the role of DNA.
Carries genetic information, determines
our inherited characteristics.
Describe the structure of RNA.
Made up of a ribose sugar, a phosphate
group, and one of four organic bases
(A,C,G,U). It is single stranded.
Describe the role of RNA.
Transfers genetic information from DNA
to ribosomes for protein synthesis.
Which bases are purine and which are pyrimidine?
Purine (double ring) = adenine, guanine.
Pyrimidine (single ring) = cytosine,
thymine, uracil.
How is DNA in eukaryotic cells different from in
prokaryotic cells?
● Eukaryotic cells= found in nucleus, long and
linear. Associated with histone proteins to form
chromosomes. Mitochondria and chloroplasts
contain prokaryotic-like DNA.
● Prokaryotic cells= short and circular. Not
associated with proteins
What is the genetic code?
The order of bases on DNA. Consists of
codons (triplets of bases that code for a
particular amino acid).
Identify features of the genetic code.
● Non-overlapping= each triplet is only read once.
● Degenerate= more than one triplet codes for the
same amino acid (64 possible triplets for 20
amino acids).
● Universal= same bases and sequences used by
all species.
What is a gene?
A sequence of bases on a DNA molecule
that codes for a specific sequence of
amino acids to make a polypeptide. Can
also code for functional RNA
What is a locus?
The fixed position on a DNA molecule
occupied by a gene.
What is an allele?
Different versions of the same gene,
found at the same locus on a
chromosome.
What are exons and introns?
Exons= regions of DNA that code for
amino acid sequences. Separated by
one or more introns.
Introns= regions of DNA that do not code
for anything.
Where are introns found?
Inbetween exons &
within genes
What is the genome?
The complete set of genetic information
contained in the cells of an organism
What is the proteome?
The complete set of proteins that can be
produced by a cell.
Describe the structure of messenger RNA (mRNA).
A long, single strand. Its base sequence
is complementary to the DNA it was
transcribed from.
Suggest advantages of using mRNA rather than
DNA for translation.
● shorter & contains uracil = breaks down
quickly so no excess polypeptide forms
● single-stranded & linear = ribosome moves
along strand & tRNA binds to exposed bases
● contains no introns
Describe the structure of transfer RNA (tRNA).
A single strand of around 80 nucleotides
that is folded over into a clover leaf
shape. On one end is an anti-codon, on
the opposite end is an amino acid
binding site.
What is produced by transcription?
mRNA
Where does transcription take place?
In the nucleus.
Outline the process of transcription.
● DNA uncoils into two strands with
exposed bases. One used as a template.
● Free nucleotides line up next to their
complementary bases, and are joined
together by RNA polymerase.
What happens to mRNA after transcription?
In eukaryotic cells, pre-mRNA must be
spliced to remove introns, leaving only
the coding regions. Then it moves out of
the nucleus and attaches to a ribosome
