Chapter 1 Flashcards
what are polypeptides?
the basic component of all proteins
where are DNA molecules found?
in eukaryotes: in the chromosomes in the nucleus, but also in the mitochondrion
what are the two broad classes of RNA?
w/o functions
- coding/messenger RNA
- noncoding RNA
what does coding RNA do?
from nucleus/mitochondria?
coding/messenger RNA
> creates polypeptide sequence when decoded
> made in nucleus: needs to be exported to cytoplasm to make proteins
> made in mitochondria: used to make proteins within those organelles
what is the function of non coding RNA?
non coding RNA
> do not code for proteins
> often involved in assisting the expression of other genes
> this may involve catalytic RNA molecules (ribozymes)
what is the general flow of genetic information?
DNA > RNA > polypeptide
what are two processes central in all cellular organisms?
- transcription
> DNA is used by RNA polymerase as template for synthesizing one of many different types of RNA
- translation
> mRNA is decoded to make polypeptides
> at ribosomes (large RNA protein complexes found in cytoplasm)
how is genetic information encoded/decoded?
genetic information is encoded in the linear sequence of nucleotides in DNA
> and decoded in groups of three nucleotides at a time (triplets)
> this is in turn decoded in groups of three nucleotides (codons)
what is the structure of both DNA and RNA?
difference?
large polymers with long linear backbones of alternating residues of a phosphate and a five-carbon sugar
> attached to each sugar is nitrogenous base
> DNA: sugar is deoxyribose
> RNA: sugar is ribose
what 4 types of bases are found in DNA/RNA?
DNA:
- adenine
- cytosine
- guanine
- thymine
RNA:
- adenine
- cytosine
- guanine
- uracil
how to divided bases into two classes?
bases
- purines (A and G)
> have two interlocked rings
- pyrimides (C, T, and U)
> have a single ring
what is a nucleoside?
carbon attached to the carbon 1 (one prime) of the sugar
what is nucleotide?
nucleotide
> a nucleoside with a phosphate group attached at the 5 or 3 prime carbon of the sugar is the basic repeat unit of a DNA strand
how are the sugar residues linked in the backbone?
linked by 3,5 phosphodiester bonds
> phosphate links the 3’ carbon atom of one sugar to the 5’ carbon atom of the next sugar
what bonds create the DNA helix?
two strands of DNA are held together by hydrogen bonds to form a duplex
according to which rule do the base pairs form?
according to the Watson Crick rules
> A pairs with T
> G pairs with C
why are the two DNA strands in a duplex described as anti-parallel?
the 5’ -> 3’ direction of the one strand is the opposite to that of its partner
why is DNA replication called semi-conservative?
each daughter DNA duplex contains one srand from the parent molecule and one newly synthesized strand
what are the two different types of daughter strands?
leading strand
> 5’ -> 3’ growth direction
lagging stand
> 3’ -> 5’ growth direction
what is the difference in growth between the leading and lagging strand?
leading always has a free 3’ hydroxyl group
> allows continuous growth in the same direction as replication fork moves
lagging strand in opposite direction of replication fork
> making of DNA segments (Okazaki fragments)
> fragments joint together to form complete DNA strand
>>> DNA synthesis is semi- discontinuous
what are “housekeeping genes?
what are other types of genes?
housekeeping genes:
> those genes need to be expressed in essentially all cells
other genes may be tissue specific, or time-specific
> time specific (cell cycle or stage of development)
RNA transcription:
> what is the non template strand also called?
> what is the template strand also called?
template strand: antisense strand
> complementary to the RNA strand that is being synthesized
non template strand: sense strand
> is identical to the RNA strand being synthsized, exept for T replacing U
how many hydrogen bonds has G-C basepair?
how many hydrogen bonds has A-T basepair?
G-C has 3 hydrogen bonds
A-T has 2 hydrogen bonds
transcription factors are called …-acting?
promoters are called …-acting?
why?
transcription factors: trans- acting
promoters: cis- acting
>> transcription factors are produced by remote genes and have to migrate to their sites of actiong
>> promotors are located on the same DNA molecule as the genes that they regulate
