WEEK 5 Flashcards
(33 cards)
What is the definition of a gene?
A gene is a basic unit of inheritance—an instruction for a heritable trait passed from generation to generation. (Slide 3)
What is a trait?
A heritable physical or physiological characteristic, such as the ability to taste or flower color. (Slide 4)
What do flower pigments, shriveled peas, and taste receptors have in common?
They all involve proteins—either enzymes or receptors—coded by genes. (Slide 5)
What idea was supported by the Beadle & Tatum experiments?
The concept that one gene codes for one protein (enzyme). (Slide 5)
What organism did Beadle and Tatum study, and what did it synthesize?
Neurospora crassa, a mold that synthesizes all molecules it needs, including amino acids like arginine. (Slide 6)
What was discovered in the Beadle and Tatum experiment with arginine biosynthesis?
Three mutant strains each had a defect in a different gene in the arginine synthesis pathway. (Slides 6–10)
What is the one gene–one protein hypothesis?
Each gene encodes a specific enzyme that contributes to a particular step in a metabolic pathway. (Slide 11)
What is the Central Dogma of Molecular Biology?
DNA → mRNA → Protein; genes encode proteins that determine traits. (Slide 12)
What is the molecular nature of a gene?
A gene is made of DNA and is composed of nucleotides. (Slide 12)
How many genes are in the human genome, and what is the average protein length?
~21,000 genes; average protein length is ~370 amino acids. (Slide 13)
Why is protein-coding DNA less than 1% of the human genome?
Because not all DNA codes for proteins—some regions regulate expression or serve other roles. (Slide 13)
What are the two main regions of a gene?
The promoter (control region) and the coding region. (Slide 14)
What does the promoter region of a gene do?
It controls when, where, and how much of a gene product is made. (Slide 14)
What is the molecular location of a gene?
A gene is a segment located linearly along a DNA molecule. (Slide 15)
Why must DNA be compacted?
Because DNA is ~1 meter long and must fit into a tiny nucleus. (Slide 16)
What are histones?
Positively charged proteins around which DNA wraps, forming chromatin. (Slide 17)
What is chromatin?
A complex of DNA and histone proteins that enables DNA compaction. (Slide 17)
What is a nucleosome?
A unit of chromatin composed of DNA wrapped around a histone octamer. (Slide 17)
What role do histone tail modifications play?
They influence transcriptional activity of associated DNA. (Slide 17)
Why is DNA compaction a problem for gene expression?
It can prevent access of transcription machinery to the gene. (Slide 18)
What are euchromatin and heterochromatin?
Euchromatin is relaxed and transcriptionally active; heterochromatin is compact and silent. (Slide 18)
Where are genes more likely to be located: euchromatin or heterochromatin?
Euchromatin. (Slide 18)
What is a chromosome?
A highly compacted structure of chromatin that carries genetic information. (Slide 19)
How is DNA further compacted after forming chromatin?
By multiple levels of compaction resulting in chromosomes. (Slide 19)
