Bio HSC Questions

[~Fire Jade~]

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Hey guys, found a stack of questions I *couldn't* do...which is sorta streesful cos it's like very close to the HSC...

1. Are homeotic genes, homeobox genes and the gene homologue the same thing? Any info on this would be great!

2. Also, I'm not really sure about DNA Fingerprinting and variable genes in 9.2.4 in the biology syllabus....Any ideas

3. What the hell are transposable genetics?

4. Explain difference in gene and point mutations for me, please?

Ugh...I'm so stupid...must need further research. Now.
Thanks

[schmani]

Originally Posted by ~Fire Jade~

Hey guys, found a stack of questions I *couldn't* do...which is sorta streesful cos it's like very close to the HSC...

1. Are homeotic genes, homeobox genes and the gene homologue the same thing? Any info on this would be great!

2. Also, I'm not really sure about DNA Fingerprinting and variable genes in 9.2.4 in the biology syllabus....Any ideas

3. What the hell are transposable genetics?

4. Explain difference in gene and point mutations for me, please?

Ugh...I'm so stupid...must need further research. Now.
Thanks

1. A gene homologue is a group of genes that code for the same function in different species. Where as a homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of development; 180 base pairs in homeotic genes (control a large number of other genes in determining the identity of segments - wings, legs etc)


2. 9.2.4 - eg) Coat colour of rabbit. 4 alleles:

- C = agouti (grey)
- Cch = chinchilla (speckled grey)
- Ch = himalayan (white with black ears, nose, feet, tail)
- c = albino

Simple pattern of domiance: C>Cch>ch>c

DNA fingerprinting:
Identifies combinations of DNA sequences that tend to vary greatly between individuals.

Microsatellites = variable DNA regions with repeated sequences near ends of chromosomes.

Identify microsatellite repeat sequences (Band in DNA fingerprint are inherited - 1/2 from each parent in Mendelian manner.) --> use restriction enzyme to cut out microsatellites from many locations within the chromosomes. Amplify using PCR then use gel electrophoresis to separate - radioactive probes show up as dark bands.

Then this is compared with a control/known sample of where bands exist along with other DNA samples (ie paternity tests or suspect DNA from crime scenes)

3. Transposable genes (known as 'Jumping Genes')
Segments of DNA which code for an enzyme that can move the segments directly from one chromosome to another. A transposon may stay in one position for several generations and then suddenly move to a new location. They can sometimes be inserted into another gene where it can cause a mutation.

Impact on Genome:
Can cause a mutation by being inserted into another gene. They lead to variation in genome – new base sequence combination. In bacteria play a role in the rapid spread of gene through bacterial population. Therefore natural selection can be accelerated by plasmids inserting transposons.

4. Do you mean the difference between mutations of chromosomes and mutations of genes? Mutations of genes and point mutations are exactly the same thing.
Mutations of chromosomes:
rearrangements: chromosomes break, reform (lost) and sequence of genes is altered.

• deletion - genes are lost from the chromosome.
• duplication - extra copies of the genes are added to a chromosome.
• Inversion - order of some genes on chromosome is reversed.
• Translocation - genes from one chromosome are added to another chromosome.

Changes in no: during meiosis if chromosomes do not separate correctly (non-disjunction) resulting in gametes that have too many chromosomes and others without enough. (homologous pairs do not separate correctly)

eg) 3 chromosomes on 21st pair = Down Syndrome
trisomy = having three homologous chromosomes instead of two.
Polyploidy = extra sets of chromosomes.

Mutations of Genes:
Base substitution: one base in the DNA substitutes another - the DNA sequence codes for a different mRNA, which codes for a different sequence of amino acids and polypeptides. Only 1 codon in the DNA is altered - one amino acid different. It can have a major impact or little effect.

• eg) Sickle cell anemia - inherited disease, change cause one of the polypetides to be wrong and the RBC curl up upon themselves.

Frameshift: If a base is deleted or added to the DNA it changes all or most of the codons - after the change, alters the sequence; code for many amino acides and polypeptides altered.

• eg) Muscular Distrophy - Duchennes. Sex linked, normally codes for a protein dystrophin - non-functional, inactive protein.

..........

I hope these are the answers you were looking for.