a few questions!! 9.4 mainly (1 Viewer)

[melimoo]

4.2 - outline, using a simple model, the process by which DNA controls the production of polypeptides

4.4 - explain how mutations in DNA may lead to the generation of new alleles

4.5 - discuss evidence for the mutagenic nature of radiation

4.6 - explain how an understanding of the source of variation in organisms has provided support for Darwin's theory of evolution by natural selection

HUH??? please help with what u can - exam tomorrow, so screwed...hehe oh well..i'm realying mainly on general knowledge and common sense
thanks

 

[bluesky100]

4.2 - outline, using a simple model, the process by which DNA controls the production of polypeptides

Polypeptide synthesis involves a type of nucleic acid, called RNA (ribonucleic acid). RNA is the intermediary between DNA and polypeptide synthesis. It is a single strand of nucleotide bases. It has ribose sugar and the nitrogen base, thymine, is replaced by uracil which bonds with adenine.
There are two types of RNA that are involved in polypeptide synthesis, messenger RNA (mRNA) and transfer RNA (tRNA).

In the nucleus, the double stranded DNA molecules unzip and the DNA code is transcribed into the single stranded mRNA molecule. The mRNA moves out of the nucleus into the cytoplasm and attaches to a ribosome. In the cytoplasm, the mRNA is translated into amino acids.

At the ribosome, the messenger RNA lines up forming a template. A group of three bases, called a codon, codes for a specific amino acid. There are codes that start and stop the chain formation. AUG is the starting point for translation.

tRNA has an anticodon (a non-amino acid forming codon) on one end and an amino acid on the other. A polypeptide is formed as each amino acid is added from tRNA to a chain following the sequence on the mRNA.

4.4 - explain how mutations in DNA may lead to the generation of new alleles

- Any change in the base sequence in DNA results in changes to the polypeptides that are produced and is a source of new alleles.
- To produce changes in alleles, the mutation must occur in the sex cells of the organism which are then passed on to the next generation.

4.5 - discuss evidence for the mutagenic nature of radiation

There is much evidence for the mutagenic nature of radiation. Environmental factors that may increase the rate of mutation include X-rays, radiation from atomic bombs and ultraviolet light.
A mutagen is a natural or human-made agent (physical or chemical) which can alter the structure or sequence of DNA. Mutagens can be carcinogens (cancer causing) or teratogens (birth defects causing).

Radiation was the first mutagenic agent known. Its effects on genes were first noticed in the 1920's.When X-rays were first discovered, they were thought to be harmless and were a great novelty. You could even buy an “X-ray machine” for your home for entertainment. Most of the first generation of scientists who worked with radiation died of cancer. Famous examples are Marie Curie and her daughter who both died of leukaemia.
Hans Muller received the Nobel Prize in 1927 for showing that genes had the ability to mutate when exposed to X-rays. Beadle and Tatum used X-rays to produce mutations in bread mould in the formulation of their “one – gene one – polypeptide” hypothesis.

The atomic bombs dropped on Hiroshima and Nagasaki also increased the evidence for mutations caused by radiation. There was a tenfold increase in cancer deaths directly after the bombs were dropped.
Mutagens may cause death in the individual but unless they affect the sex cells the effect is not passed on to the next generation.

4.6 - explain how an understanding of the source of variation in organisms has provided support for Darwin's theory of evolution by natural selection

One of the foundation pillars for the theory of evolution is the variation that occurs among individual members of a species. It is this variation that selection acts upon. Mutation of DNA provides a source of variation thus supporting Darwin's theory of evolution.

I hope this helps you understand the questions - good luck with you exam!!

 

[melimoo]

thanx alot!!! rep rep rep

 

[Anthrax]

thanx alot!!! rep rep rep

lol before you ask anymore questions

http://hsc.csu.edu.au/biology/core/blueprint/