Chapter 12 Flashcards
What is the chromosomal basis of Mendel’s laws?
The chromosomal basis of Mendel’s laws lies in the segregation and independent assortment of alleles during meiosis. Genes are located on chromosomes, and the behavior of chromosomes during meiosis explains the inheritance patterns observed by Mendel.
Who was Thomas Hunt Morgan and how was his work important to the scientific community?
Thomas Hunt Morgan was a pioneering geneticist who extensively studied fruit flies (Drosophila melanogaster). His work provided experimental evidence for the chromosomal theory of inheritance, demonstrating the linkage of genes on chromosomes and the role of sex chromosomes in inheritance.
How does the behavior of a gene’s alleles correlate with the behavior of a chromosome pair?
The behavior of a gene’s alleles correlates with the behavior of a chromosome pair during meiosis. Alleles segregate to different gametes, and their independent assortment is influenced by the random alignment and separation of homologous chromosomes.
What is the chromosomal basis of sex?
The chromosomal basis of sex involves the presence of sex chromosomes (X and Y). In humans, females have two X chromosomes (XX), and males have one X and one Y chromosome (XY).
How does the inheritance of sex-linked traits work?
Sex-linked traits are located on the sex chromosomes. In humans, X-linked traits are more common, and they are inherited differently in males and females due to the presence of only one X chromosome in males.
What is x-inactivation and how does this relate to Barr bodies?
X-inactivation is a process in which one of the two X chromosomes in females becomes transcriptionally inactive. Barr bodies are condensed, inactivated X chromosomes found in the nuclei of female cells, ensuring gene dosage compensation.
How does linkage of genes affect inheritance?
Linked genes are located on the same chromosome, and their inheritance is not independent due to physical linkage. The closer genes are on a chromosome, the less likely they are to undergo recombination.
What is the difference between parental types and recombinant types?
Parental types have combinations of alleles that match one of the original parental combinations. Recombinant types result from genetic recombination and have novel combinations of alleles not present in the parents.
How does a new combination of alleles affect natural selection?
New combinations of alleles resulting from genetic recombination contribute to genetic variation. Natural selection acts on this variation, favoring advantageous traits and influencing the evolution of populations.
What are recombination frequencies and how do we calculate them?
Recombination frequencies represent the likelihood of recombination between two genes. They are calculated by determining the percentage of recombinant offspring in a genetic cross.
What can alteration to the number or structure of chromosomes do to an individual?
Alterations to the number or structure of chromosomes can lead to genetic disorders, developmental abnormalities, or infertility in individuals.
What are examples of different types of alterations to chromosome structure?
Examples include deletions, duplications, inversions, and translocations, which can disrupt normal gene function and lead to various genetic disorders.
What are some examples of disorders associated with alteration to the number or structure of chromosomes?
Examples include Down syndrome (trisomy 21), Turner syndrome (monosomy X), and various cancers resulting from chromosomal translocations or deletions.
Heterogametic
Refers to an individual whose sex chromosomes are different, such as males in many species (XY in mammals).
Homogametic:
Refers to an individual whose sex chromosomes are the same, such as females in many species (XX in mammals).
Sex Linkage
The inheritance pattern of genes located on sex chromosomes, typically X-linked or Y-linked
Autosome
Any chromosome other than a sex chromosome. they carry genes for non-sex-related traits
Wild-type
The standard or normal phenotype or genotype observed in a population under natural conditions
Mutant
An individual or genotype with a variation from the wild-type due to a genetic mutation
SRY Gene
The Sex-determining Region Y gene, which plays a key role in initiating male sex determination in mammals
Sex-limited traits
Traits that are expressed only in one sex, despite both sexes having the genes for that trait
Sex influenced traits
Traits that are influenced by the sex of the individual, leading to different phenotypic expressions in males and females
X-linked
Genes located on the X chromosome. Inheritances of X-linked traits often show different patterns in males an females
X-Inactivation
A process in females where one of the X chromosomes becomes transcriptionally inactive to compensate for gene dosage
Barr body
A condensed, inactivated X chromosome found in the nuclei of female mammalian cells undergoing X-inactivation.
Non Disjunction
The failure (or successful separation) of homologous chromosomes or sister chromatids during cell division.
Aneuploidy
Abnormal chromosome number resulting from the gain or loss of one or more chromosomes.
Trisomy
A genetic condition where an individual has three copies of a particular chromosome instead of the usual two.
Recombinants
Offspring with a combination of alleles different from those of the parental generation due to genetic recombination.
Recombination Frequency
The percentage of recombinant offspring in a genetic cross, indicating the likelihood of recombination between genes.
Parentals
Offspring with a combination of alleles identical to those of the parental generation in a genetic cross.
Monosomy
A genetic condition where an individual lacks one chromosome from the normal diploid number.
