SB3 -Genetics

Advantages and Disadvantages of Sexual and Asexual Reproduction

Advantage of sexual:

Genetic variation

Disadvantage of sexual:

Requires a mate

Advantage of asexual:

Doesn’t require a mate

Disadvantage of asexual:

No / little genetic variation

What is DNA?

DNA is made up of double helix strands made up of complementary base pairs held together by weak hydrogen bonds and nucleotides that consist of a sugar and a phosphate group with one of 4 different bases attached to the sugar.

What is a gene and a genome?

A gene is a section of DNA that codes for a specific protein. Genome is the entire DNA of an organism.

How can DNA be extracted from food?

1. Mash the fruit in a plastic bag.

2. Use detergent, protease and salt water to break down cell membranes and release the DNA.

3. Filter the fruit mixture.

4. Pour ice-cold ethanol to precipitate the DNA making it visible as white strands.

Protein synthesis

Step1: Transcription

1. DNA unzips

2. RNA polymerase uses one DNA strand as a template

3. Complementary mRNA is made

4. mRNA leaves nucleus into cytoplasm.

Step2 : Translation

1. mRNA attaches to a ribosome.

2. mRNA attaches to a ribosome.

3. Anticodons match codons on mRNA.

4. Amino acids join by peptide bonds.

5. Chain folds into a protein.

How does genetic variation at the non-coding region affect the phenotype?

It means that the RNA polymerase doesn’t bind to the gene so less proteins that the gene was coding for would be produced.

How does genetic variation at the coding region affect the phenotype?

It means that the sequence of amino acids would change which would affect its 3D structure and function.

Gregor mendel

Alleles

Different versions of the same gene.

What is codominance and example for it ?

It is a genetic trait where both alleles for a gene are fully and equally expressed in the phenotype. AB blood type.

What letter refers to blood type?

I

Explain how sex-linked genetic disorders are inherited?

1. Some alleles are only found on sex chromosomes X and Y.

2. Majority of sex-linked disorders are found at the X chromosome.

3. This means a male is more likely to get an X-linked recessive disease since females have two X chromosomes to mask the effect of the recessive allele. Males only have one X chromosome so if they have one recessive allele that causes the disorder it will be shown in the phenotype.

What 2 variations are there?

1. Genetic

2. Environmental

What are benefits of the human genome project?

1. They enable personalised medicine.

2. Identifies mutation

How does genetic variation occur?

Mutation

How often do gentetic mutations affect the phenotype?

Rarely