Biological Proccesses - Genetics

8 important questions on Biological Proccesses - Genetics

Mendel's 1st law of segregation (4 postulates)

  1. Genes exist in alternative forms (alleles), that controls a specific trait
  2. An organism has 2 alleles for each gene, one from each parent
  3. The 2 alleles segregate during meiosis, forming gametes that carry only one allele for any given inherited trait
  4. For every 2 alleles, one is dominant and 1 is recessive. Only the dominant allele will be expressed

Mendel's second law of independent assortment

The inheritance of one trait is completely independent of the inheritance of another trait.

Ex: plant's color is independent of the the plant being a dwarf

** in non-mendelian genetics due to crossing over we see that some traits tend to be linked together, but they are still able to be separated and occur without the other

2 common sex linked conditions:

Color-blindness and hemophilia

Occur because they are recessive on the X chromosome, and men do not have another X chromosome that could carry a dominant allele to mask the recessive gene
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Can men with sex-linked conditions pass the condition on to their offspring?

They can not pass the condition on to their male offspring, but will pass it on to all of their daughters. If the daughter also received the gene from their mother, they will have the trait. Half of that daughter's sons will also receive the trait.

Environmental affect on gene expression

Some genes are linked to environment.
Ex: fur color in hares based on temp., crooked/ straight wings in drosophila based on temp.

Cytoplasmic inheritance of genes

Heredity of genes outside of the nucleus

DNA is found in the mitochondria, and in cytoplasma (plasmids). These DNA molecules can interact with nuclear genes and can determine characteristics of organelles. Bacteria can regulate drug resistance by the use of plasmids in the cytoplasm which can be passed from one cell to another via conjugation.

Inducible gene regulation

System requires the presence of an inducer for transcription to occur.

Repressor is always bound to the operator unless an inducer binds to the repressor, changing its shape and removing it from the operator.

Repressible gene regulation

In a constant state of transcription unless a repressor is bound.

Repressor is always inactive unless it is bound by a corepressor. This changes the repressor's conformation, allowing binding to the operator and preventing transcription.

Corepressors are often end products of the pathway being controlled.

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