case 5 Flashcards
complex genetic
What are mendelian laws?
The three main laws are:
1. -Law of segregation: each individual has two alleles for each gene, and these alleles segregate (separate) during gamete formation, thus offsprings inherit one allele from each parent.
2. -Law of independent Assortment: genes for different traits assort independently of one another during gamete formation, provided the genes are not linked (genes are located on different chromosomes or alternatively genes are far apart on the on the same chromosome). This means the inheritance of one trait generally does not affect the inheritance of another.
3. -Law of dominance: In a heterozygous individual one allele may be dominant over another, masking its expression.
what is gene linkage?
linked genes are located close together on the same chromosome and tend to be inherited together. They do not assort independently unless crossing over occurs.
genes for flower colour and pollen shape in peas may be linked if they are on the same chromosome.
What is incomplete dominance
allele is completely dominant, resulting in an intermediate phenotype.
Example; when a red-flowered plant (RR) is crossed with a white-flowered plant (WW), the offprints (RW) have pink flowers
What is codominance?
both alleles are expressed simultaneously in the heterozygote.
Example; in human blood types, the AB blood group is an example of codominance, where both A and B are fully expressed.
what are sex-linked genes?
Genes located on sex chromosomes (X or Y) are called sex-linked genes. Most commonly, X-linked genes show different patterns of inheritance in males and females.
Hemophilia and color blindness are X-linked recessive disorders. Males (XY) are more likely to express X-linked recessive conditions because they have only one X chromosome
What is pleiotropy?
a single gene influences multiple phenotypic traits
the PKU (Phenylketonuria) gene affects multiple systems in the body, leading to intellectual disability, skin pigmentation changes, and more if untreated.
what is epistasis?
the expression of one gene is affected by one or more other genes. Essentially one gene can mask or modify the expression of another gene.
in labrador retriever, coat colour is determined by two genes. One gene determines pigment (black or brown), while another gene can suppress pigment production entirely, leading to a yellow coat.
what is epigenetics?
volve modifications in gene expression that do not alter the underlying DNA sequence. Factors like DNA methylation and histone modification can regulate genes, often in response to environmental conditions.
identical twins may have differences in gene expression due to epigenetic changes despite having the same DNA sequence.
what is singlenucleotide polymorhism(SNPs)
are variations in single nucleotide at specific position in the genome among individuals.
Example: for a given position in DNA, one may have an ‘’A’’ another may have a ‘’G’’ and a third may have a ‘’C’’. these variations do not always cause disease but can contribute to differences in traits, such as drug response or disease susceptibility.
What is crossing over?
During the prophase of meiosis 1, homologous chromosomes may exchange segments in a process called crossing over. This can separate linked genes, resulting in new combinations.
What is GWAS?
Genome Analysis: GWAS scans the entire genome to identify which SNPs are statistically associated with the trait in question.
What are complex traits?
Complex traits such as height or intelligence is influenced by multiple genes (polygenetic trait) and environmental factors. Unlike mendelian traits, which are controlled by a single gene, complex traits result from the interplay of many genes and various non-genetic factors.
Explain “Sanger” sequencing
We could see base pair by base pair for the first time.
Explain PCR
You take DNA you denaturation annealing Elongation it until you get a lot of copies . (Kary Mullis 1981)
Explain GWAS
Uses PCR and Micro-array technology. It resulted in a genome-wide genotypes.
