Interview
Genetics Unit
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Interview of 24 pages for the course Biology at 12th Grade (GENETICS)
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Phenotypes- The characteristic or trait of an organismGenotypes- a symbolic representation of the pair of alleles that an organism has (BB, Bb, bb)
Dominant allele- has the same effect on phenotype no matter the allele pairing
Recessive allele- An allele that affects the phenotypes only when paired with another recessive allele
Co-dominant alleles- pairs of alleles that affect the phenotype when present (a black and white chicken
making a speckled chicken)
Homozygous- two identical alleles of a gene BB
Heterozygous- two different alleles of a gene Bb
Carrier- A person who has a recessive allele but still has the copy
Test-cross- Testing a suspected heterozygote by crossing it with a known homozygous recessive
individual
Autosomal Recessive Disease- a genetic syndrome resulting from the inheritance of two recessive
alleles for a gene found on one of the 22 chromosomes (sickle cell anemia, albinism, cystic fibrosis,
Phenylkentonaria)
Karyogram-chromosomes are stained and photographed to generate a visual profile Karyotype-
The term also refers to a laboratory-produced image of a person's chromosomes isolated from an
individual cell and arranged in numerical order
Gene- A heritable factor that controls specific characteristics. It is also a section of DNA that codes for a
polypeptide.
Allele- Different forms of variants of a specific gene
Genome- The whole of the genetic information of an organism
Gene mutation- When the nucleotide base letter sequence of the DNA is changed
Base Substitution Mutation- When a single letter in the DNA sequence is replaced with a different
letter.
Frameshift Mutation- A single letter in the DNA sequence is added or deleted
Gene Locus- A specific position of a gene on a chromosome
Human Genome Project- An international research project that led to the mapping/sequencing of the
entire genetic material of a human being.
Gene mapping- the process of determining the locus for a particular biological trait
Non-Disjunction: When chromosomes do not separate properly during meiosis resulting in a gamete
either having an extra chromosome(trisomy)or missing a chromosome (monosomy)
Somatic mutations – occur in a single body cell and cannot be inherited (only tissues derived from the
mutated cell are affected)
,Germline mutations – occur in gametes and can be passed onto offspring (every cell in the entire
organism will be affected)
, 3.1
DNA is the genetic blueprint which codes for, and determines, the characteristics of an organism
includes the physical, behavioural and physiological features of the organism
DNA is packaged and organized into discrete structures called chromosomes
A gene is a sequence of DNA that encodes for a specific trait (traits may also be influenced by
multiple genes)
The position of a gene on a particular chromosome is called the locus (plural = loci)
Alleles are alternative forms of a gene that code for the different variations of a specific trait. For
example, the gene for eye colour has alleles that encode different shades/pigments.
As alleles are alternative forms of one gene, they possess very similar gene sequences. Alleles
only differ from each other by one or a few bases.
A gene mutation is a change in the nucleotide sequence of a section of DNA coding for a specific trait
- New alleles are formed by mutation
(missense mutations) change the gene sequence to create new variations of a trait
(nonsense mutations) shortens the gene sequence to void the normal function of a trait
(silent mutations) have no effect on the functioning of the specific feature
Frameshift mutations- occur when the addition or removal of a base alters the reading frame of the gene
This change will affect every codon beyond the point of mutation and thus may dramatically
change the amino acid sequence
Point mutations are changes to one base in the DNA code and may involve either:
The substitution of a base (e.g. ATG becomes ACG)
The insertion of a base (e.g. ATG becomes ATCG)
The deletion of a base (e.g. ATG becomes AG)
The inversion of bases (e.g. ATG becomes AGT)
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