Heredity Flashcards
What is a gene?
A gene represents the genetic material on a chromosome that contains the instructions for creating a particular trait.
What is an allele?
It is one of several varieties of a gene.
What is a locus?
This refers to the location on a chromosome where a gene is located. Every gene has a unique locus on a particular chromosome.
What term describes the expression of an allele?
Phenotype
What term represents the actual alleles?
Genotype
Who is credited with the discovery of LAWS of SEGREGATION and INDEPENDENT ASSORTMENT?
Gregory Mendel
Describe the Law of Segregation
Separation of alleles and chromosomes to individual gametes (meiosis)
What is independent assortment?
The independent assortment of homologs in metaphase I as they are separated into opposite poles. This assortment is independent because the migration of homologues within one pair of homologous chromosomes does not influence the migration of other homologues.
When do you utilize a monohybrid cross?
Investigation of ONE trait
When do you utilize a dihybrid cross?
Ingestivation of TWO traits.
Inheritance pattern in which one allele is expressed as dominant to a second allele.
Complete (or full) dominance
Describe the genotypic frequencies resulting from the cross (TT x tt)
4/4 Tt
Describe the genotypic frequencies resulting from a monohybrid cross of two heterozygotes.
(Tt x Tt), we see 1/4 TT + 1/2 Tt + 1/4 tt
In a dihybrid cross of homozygous dominant and homozygous recessive plants with two traits, what are the genotypes of F1 generation? (YYRR x yyrr)
16/16 heterozygous YyRr
Describe the genotypic frequencies of the F2 generation (F1: YyRr)
1: YYRR
2: YYRr
2: YyRR
4: YyRr
1: yyRR
2: yyRr
1: YYrr
2: YyRr
1: yyrr
Describe the phenotypic frequencies of the F2 generation (F1: YyRr)
9
1:2:2:4
3
1:2
3
1:2
1
1
Imagine a continuum of inheritance patterns. Identify each extreme and one in between.
Complete dominance would be one extreme in which one allele is expressed. At the other extreme is Codominance, in which both alleles are expressed. In between is Incomplete dominance in which there is a blending of two alleles producing an intermediate phenotype.
How many possible genotypes/genotypes for blood types?
6 genotypes, 4 genotypes
The expression of both kinds of proteins in blood AB is an example of which inheritance pattern?
Codominance
The heights of humans are displayed as a _______ _________ from very short to very tall. This is usually a result of ________ __________.
Continuous Variation; Polygenic Inheritance
What is polygenic inheritance?
The interaction of many genes to shape a single phenotype
What are linked genes?
Genes that reside on the same chromosome and cannot segregate independently because they are physically connected. They do not obey the law of independent assortment and are usually inherited together.
Describe the function of SRY
Sex-determining region of Y regulates gene activities on other chromosomes which stimulate the development of male characteristics….resulting in traits that are sex-limited
Failure of one or more chromosome pairs of chromatids to separate and move to opposite poles during meiosis or mitosis
Nondisjunction
How does nondisjunction occur in meiosis?
Failure of homologues to separate in anaphase I and failure of chromosomes to separate into chromatids in anaphase II
How does nondisjunction occur in mitosis?
Same way in anaphase II
How does mosaicism occur?
During embryonic development, nondisjunction results in cells with extra or missing chromosome - cells that have descended from a cell where nondisjunction occured
What happens if all chromosomes undergo meiotic nondisjunction?
Polyploidy. A polyploidy zygote can result from two polyploidy parents. This is common in plants.
When a single nucleotide in the DNA of a gene is incorrect, this is referred to as __________
Point mutation
What causes sickle-cell disease?
nucleotide substitution resulting in production of defective hemoglobin that become sickle-shaped when low-oxygen conditions occur.
What happens in an individual homozygous for the allele for (sickle-cell disease)?
They suffer inadequate oxygen supply which can lead to organ damage, bone abnormalities, and impaired mental functioning
Describe symptoms of individuals with sickle-cell trait
Generally asymptomatic as the normal allele is sufficient to produce adequate amounts of normal hemoglobin
What causes Tay-Sachs disease?
Usually caused by a nucleotide insertion - which results in lysosomes lacking the enzymes needed to metabolize glycolipids. As a result, these fats accumulate in nerve cells of the brain - causing them to die - causing early childhood death
What is Turner syndrome?
XO - occurs in females as a result of nondisjunction of sex chromosomes. (“Turner was my ex ho”)
What is Klinefelter syndrome?
XXY - males have an extra X chromosome as a result of nondisjunction of sex chromosomes from parents. (3 syllables, like 3 chromosomes)
What causes Huntington’s disease?
Hint: Hunting-T-O-N
(“Three Oligodendrocytes Nondisjunction”) Insertion of multiple repeats of 3 nucleotides. This mutant gene codes for a defective enzyme, which results in the death of nerve cells in the brain.
Describe chromosomal aberrations
changes in chromosome segments: (e.g. Inversions (Paracentric vs Pericentric), Translocations, Duplications)
