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Flashcards in Genetics II Deck (26):

What is incomplete dominance?

? Is when both alleles for a specific gene is expressed in a heterozygous individual. Neither allele is considered dominant or recessive and hence the characteristic expressed is a ‘blend’ or ‘mixture’ of both characteristics.


What is co-dominance?

Is when both alleles for a specific gene is expressed in a heterozygous individual. Neither allele is considered dominant or recessive and hence the characteristic expressed are two characteristic co- existing with another, not blended.


What is a pedigree?

A flow chart that shows the relationship within a family over generations. And is useful for detecting patterns in a genetic disorder and identifying genotypes of family members.


What is simple dominance?

For the first 22 pairs of chromosomes as they have the exact same type of gene, patterns of inheritance are identical for both genders. There is an equal chance for both genders to acquire a specific gene whether it be a characteristic or a disease.


What are x- linked genes?

Genes that code for characteristics that are only on the x- chromosome.


Explain which gender suffers the most genetic disorders and why?

Male suffers the most genetic disorders as they can’t have a dominant genes to mask the recessive.


Define mutations:

-Alteration to genes
-Occur naturally but are rare (1 in a mil)
-Has consequences to the organism’s characteristics



- Affected gene stopped the production of melanin, a gene which gives skin and hair its colour
-Therefore, no pigmentation
-CONSEQUENCE: appears to have white- pink skin, hair and eyes


Down- syndrome

- Person with an extra chromosome on their 21st chromosome, therefore has three chromosomes instead of having a pair
- CONSEQUENCE: affects growth and development


List some examples of bad mutations?

-Cancer, by tar in cigarettes
-Or by UV rays which damages the DNA


List some examples of good mutations?

-Seedless fruit, disease- resistant crops


How are mutations inherited by their offspring?

Mutation that occur in sex cells can be passed down


What are genetic mutations?

Involve a change in DNA due to external factors such as UV/ radiation/ chemicals


What does mutated codons include?

-Code for the same amino acid, in this case there is no change
-Code for a different amino acid- in this case there might be a slight change
-Code for a ‘stop’- in this case cause drastic changes as it shortens the polypeptide


What are chromosomal mutations?

Include variations in the number of chromosomes


What is a genome?

Complete set of genetic material existing inside an organism or cell


How does the offspring inherit characteristics?

-Since genes carry characteristics by producing proteins, these get passed down and the offspring inherit these characteristics


What are genes on a homologous pair of chromosomes said to be 'identical'?

- As they both code for different forms
- Even though one can code for blue whilst the other brown since both genes code for eye colour


What are the different form of the same known as?



Why do we have two alleles for different characteristics but only show one?

Because one allele is dominant and the other is recessive.


What does a lower case represent?

A recessive gene


What does an upper case represent?

A dominant gene


What is a genotype?

A set of alleles for that type of gene


What are the three possibilities of genotypes?

-Homozygous recessive
-Homozygous dominant


What does our genotype determine?

Our physical characteristics aka phenotype


What is a punnet square?

? A tool used to determine the possible genotype of an offspring. But to do this the genotype of the mother and father is needed.