Genetics
Different forms of a gene found at the same locus on homologous chromosomes.
What are alleles?
Genes located close together on the same chromosome that tend to be inherited together are called this.
What are linked genes?
The specific pairing between A–T and G–C explains these empirical observations first made by Chargaff.
What are Chargaff’s rules?
The physical appearance resulting from a genotype.
What is a phenotype?
In a monohybrid cross (Pp × Pp), the probability of producing a heterozygous offspring.
What is ½ or 50%?
This model explains why alleles for a heritable trait separate during gamete formation.
What is the Law of Segregation?
When chromosomes fail to separate properly during meiosis, this phenomenon occurs.
What is nondisjunction?
DNA strands run in opposite directions, a feature known by this term.
What is antiparallel orientation?
Mendel’s discovery that allele pairs separate independently during gamete formation led to this principle.
What is the Law of Independent Assortment?
A dihybrid cross between heterozygotes typically produces this phenotypic ratio if genes assort independently.
What is 9:3:3:1?
The breeding method used to determine whether a dominant phenotype is homozygous or heterozygous
What is a testcross?
This type of chromosomal alteration involves the transfer of a segment to a nonhomologous chromosome and causes chronic myeloid leukemia.
What is translocation?
Uncorrected replication errors that become permanent changes in DNA sequences are called these and serve as the raw material for evolution.
What are mutations?
This enzyme unwinds the DNA double helix at the replication fork.
What is helicase?
This genetic phenomenon occurs when one gene affects multiple traits, as in cystic fibrosis or sickle-cell disease.
What is pleiotropy?
When neither allele is completely dominant, and heterozygotes show an intermediate phenotype.
What is incomplete dominance?
In female mammals, one X chromosome is randomly inactivated during embryonic development, forming this condensed structure.
What is a Barr body?
Short segments of DNA on the lagging strand are known as these and are joined by this enzyme.
What are Okazaki fragments joined by DNA ligase?
When both alleles are fully expressed in the phenotype of a heterozygote.
What is codominance?
This molecular process is responsible for gene silencing in genomic imprinting.
What is DNA methylation?
In this type of inheritance, one gene alters or masks the expression of another gene.
What is epistasis?
Because males have only one X chromosome, they are described by this term when expressing X-linked traits.
What is hemizygous?
This enzyme relieves strain in the DNA molecule caused by unwinding during replication.
What is topoisomerase?
These repetitive sequences at the ends of eukaryotic chromosomes help protect genes from erosion during replication.
What are telomeres?
This repair mechanism removes damaged DNA sections, such as those caused by UV radiation, using a nuclease enzyme.
What is nucleotide excision repair?