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Biology: Genetics

Terms in this set (25)

Gene
sequence of DNA that codes for a protein and thus determines a trait
ex. eye color, blood type
Chromosome
coiled structure of DNA in the nucleus that contains hereditary material
Allele
when a gene mutates and takes on two or more different forms, an allele is a specific variation of a gene found at a fixed spot on a chromosome, organism inherits one allele from each parent (since chromosomes come in pairs, one from each parent)
simple traits can be either dominant or recessive
ex. blue eyes, type AB blood
Homologous
paired chromosomes (during meiosis) that have the same codes for the same traits at the same locations (same location on maternal vs paternal)
*reference to chromosome in a pair
Homozygous
both alleles (blue eyes) for the same gene (eye color) from each chromosome (one from mom, one from dad) are the same, both code for blue eyes
*reference to an individual gene
ex. RR or rr
Heterozygous
chromosome pair has two different alleles (blue eyes vs brown eyes) for same gene (eye color)
ex. Rr
Dominant Allele
an allele whose trait always shows up in the organism when the allele is present
Recessive Allele
an allele that is masked when a dominant allele is present
Genotype
an organism's genetic makeup, or allele combinations (letters)
Phenotype
the set of expressed characteristics of an individual resulting from the genotype (blue eyes)
Punnet Square
a chart that shows all the possible combinations of alleles that can result from a genetic cross
Multiple Alleles
Three or more alternative forms of a gene that can occupy the same locus (area on a chromosome where a particular gene is located)
ex. blood type (combination of A B or O)
Pleiotropy
one gene influences two or more seemingly unrelated phenotypic traits
ex. cystic fibrosis gene effects many phenotypes
Epistasis
one gene masks or interferes with the expression of another gene
ex. mice with wild type coat (AA) are dominant to solid color coat (aa) BUT the C gene is also required to produce pigment in general, so if recessive cc is present, mouse will be albino regardless of A/a interaction
Polygenic Inheritance
multiple genes determine the phenotype of a trait
ex. height is not just "tall" or "short" but rather, a variation dependent on over 400 genes, also present in weight, skin color, eye color etc
DNA Structure
two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine
Nucleotides
basic units of DNA molecule, composed of a sugar, a phosphate, and one of 4 DNA bases (bonded to the sugar)
DNA Replication
-DNA helocase breaks hydrogen bonds between base pairs in order to "unzip" the double helix
-DNA polymerase binds and coordinates "obligatory base pairing" which binds complimentary nucleotides to exposed bases of original strand
-forms new "other half" to each half of the original molecule, yields two identical DNA molecules and are ready for distribution to two daughter cells
Protein Synthesis (transcription)
occurs in the nucleus and is the process by which genetic information encoded in DNA is copied onto a strand of mRNA to direct protein synthesis
*base pairs the same but uracil is subbed for thymine
Protein Synthesis (translation)
occurs in the rough er or cytosol (wherever there are ribosomes),
mRNA slides through ribosomes in groups of 3, called codons
tRNA carries anticodons that, when bonded in order of codons, releases each next amino acid to form a chain (bonded by peptide bonds)
tRNA released by the ribosome, chain ends at a stop codon and released into the cytoplasm
Peptide Bond
the chemical bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid, releases a water molecule when bond occurs, covalent
Codon
three-nucleotide sequence on messenger RNA that codes for a single amino acid
Polypeptide
a polymer (chain) of many amino acids linked together by peptide bonds
Protein
an organic compound that is made of one or more chains of amino acids and that is a principal component of all cells (smallest is around 50 amino acids)
Amino Acid
building blocks of protein, 9 essential for life, 20 total which make up all proteins
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