Human Genetics Midterm 2025

Gene

a segment of DNA that acts as the basic unit of heredity, passed from parent to offspring

Chromatid

Huge DNA molecule, is one half of a duplicated chromosome

Centromere

the constricted region of a chromosome that links two sister chromatids together.

Allele

one of two or more versions of a gene, which is a segment of DNA that determines a specific trait (form of a trait)

Phenotype

the set of an organism's observable physical, biochemical, and behavioral characteristics

Genotype

the specific genetic makeup of an organism, which includes the combination of alleles for a particular gene or, more broadly, the entire set of genes it carries

Heterozygote

an organism that has two different alleles for a specific gene, with one allele inherited from each parent

Homozygote

an organism that has two identical alleles for a particular gene, one inherited from each parent

Amino Acid

are the subunits or building blocks that are hooked together into long protein chains, are to proteins what nucleotides are to DNA.

nucleotide

subunits that make up DNA molecules

There are four, They are adenine, guanine, cytosine and thymine.

A gene is made up of thousands of these nucleotides.

transcription

takes place in the cells nucleus, the information in one of two DNA chains serves as a guide (template) to make a complementary messenger RNA (i.e., an RNA that obeys Chargaff’s rule)

the process of creating an RNA copy of a segment of DNA. The DNA's genetic information is copied into a messenger RNA (mRNA) molecule, which is a complementary strand to the DNA template

the genetic information in a segment of DNA is copied into a new molecule of messenger RNA (mRNA)

translation

takes place in the cytoplasm of the cell, specifically on structures called ribosomes

the "reading" of the mRNA code to build a protein, which is a chain of amino acids called a polypeptide

a ribosome decodes messenger RNA (mRNA) to synthesize a chain of amino acids (a polypeptide), which then folds into a protein

Messenger RNA

the form of RNA in which genetic information transcribed from DNA as a sequence of bases is transferred to a ribosome

codon

A group of three nucleotides, specifies a particular amino acid in the protein

promoter

a specific set of nucleotides in every gene that marks the correct DNA chain for transcription

mutation

a change in an organism's DNA sequence, which can occur spontaneously or be caused by environmental factors

enzyme

Proteins that work as catylysts, speed up reactions

substrate

a substance that an enzyme acts upon to convert into a product

active site

The specific place an enzyme catalyses a reaction, has a specific shape that the substrate recognizes

hydrophobic

water hating

hydrophilic

water loving

Mendel’s 3:1

arises from a monohybrid cross between two heterozygous parents

What did Grifith’s experiments with mice demonstrate

Griffith's experiment demonstrated that bacteria can be transformed, meaning they can take up genetic material from their environment and change their characteristics

Chargaff's rule

in a double-stranded DNA molecule, the amount of adenine (A) equals the amount of thymine (T), and the amount of guanine (G) equals the amount of cytosine (C). This means the ratio of (A) to (T) is (1:1) and the ratio of (G) to (C) is (1:1), a principle crucial for the stability and structure of the DNA double helix

semiconservative replication

every time a cell divides to make a daughter cell, each DNA strand serves as a template for a new chain

Why are promoters important for transcription?

A promoter is a region of DNA where transcription of a gene is initiated. Promoters are a vital component of expression vectors because they control the binding of the RNA polymerase to DNA

exons

the coding regions of a gene that are expressed and remain in the final messenger RNA (mRNA) to be translated into a protein

introns

non-coding sequences that are removed during RNA splicing

What is meant by the statement that the genetic code is redundant?

More than one codon can specify the same amino acid

Amino acid

building block of protein, held together by peptide bonds

nucelotide

building block of dna, held together by phosphodiester bond

the ways amino acids differ from one another

The "R" group is made up of specific atoms and these differ for each amino acid. Thus, each amino acid has its own unique chemical behavior

the role of hydrogen bonds in DNA replication and RNA transcription

Hydrogen bonds play a crucial role in DNA replication and RNA transcription by temporarily holding the two DNA strands together in a double helix but being weak enough to be broken, allowing for separation

the difference between a hydrophobic and hydrophilic molecule.

A hydrophobic molecule is water hating, a hydrophilic molecule is water loving

the major roles played by proteins in cells.

provide support, transport materials, serve as biological catalysts

what enzymes do in cells

Enzymes catalyze reactions to make them go faster

how enzymes recognize their specific substrates in the active site

through a combination of complementary shape and chemical interactions within the active site, a process guided by the induced-fit model

Base-pair substitution

a genetic mutation where one nucleotide base in a DNA sequence is replaced by another

Frameshift mutation

mutation where one or more nucleotides are inserted or deleted from a DNA sequence, causing the reading frame of the gene to shift

Silent mutation

a change in the DNA sequence that does not alter the resulting amino acid sequence of a protein, thanks to the redundancy of the genetic code

Missense mutation

genetic alteration where a single DNA nucleotide change results in a different amino acid being incorporated into a protein

Nonsense mutation

a genetic change that causes a premature stop codon to be inserted into the mRNA sequence, leading to the premature termination of protein synthesis

Leaky or partial mutation 

genetic mutation that results in a partial loss of gene function, but not a complete loss

Understand what happens to the mutant protein to cause sickle cell

1) In normal individuals, the sixth triplet codon in the ɑ chain is GAG and it stands for the amino acid glutamic acid. In scd patients, a base-pair substitution has occurred and the new codon is GUG (GTG in the DNA). This triplet codon specifies the amino acid valine.

2) Valine is chemically very different than glutamic acid, This single change causes the hemoglobin molecules to clump together into a big mass of protein.

3) Because hemoglobin is the major product of erythrocytes and is made in huge quantities, this protein clumping causes the cells to become elongated and bent.

4) These cells break easily and the debris jams joints and arteries. There is also reduced ability to transport oxygen. The disease is quite painful anddebilitating.

for sickle cell, what the wild-type protein does normally in the cell

Normal Hemoglobin is the protein in red blood cells that carries oxygen from the lungs to the rest of the body. In healthy individuals, red blood cells are flexible and round, allowing them to move easily through blood vessels and deliver oxygen efficiently

How did the experiment of Avery, McCloud, and McCarty show that DNA is the hereditary material

by demonstrating that DNA from dead virulent bacteria could transform live, harmless bacteria into the virulent type

Know what happens at each division of meiosis.

During Meiosis I, homologous chromosomes pair up and then separate, reducing the chromosome number by half.

In Meiosis II, the sister chromatids within each of the two cells then separate, resulting in four haploid cells

Be able to explain how a pair of alleles goes through meiosis

A pair of alleles goes through meiosis via the segregation of homologous chromosomes in Meiosis I and the separation of sister chromatids in Meiosis II, resulting in each gamete receiving only one of the two original alleles. This is further shuffled by crossing over in Meiosis I, where homologous chromosomes exchange segments, and by independent assortment, where homologous chromosomes align and are sorted randomly into daughter cells

Understand how genetics is carried out in pea plants

cross-pollinating plants with specific, contrasting traits (like tall vs. short) and then meticulously observing and counting the traits that appear in the offspring across multiple generations

Why was each of the controls (panels A-C), for griffith’s experiment, necessary (what issue did each address)?

These controls collectively demonstrated that neither the live R bacteria nor the heat-killed S bacteria alone were lethal, providing the necessary context to interpret the crucial experimental result: when the two were mixed, the mice died, leading to the conclusion that a "transforming principle" had passed from the dead S cells to the live R cells

what kinds of chemical interactions are important in determining a protein’s shape

hydrogen bonding, ionic bonding, hydrophobic interactions, and disulfide linkages

superiority of the heterozygote

a situation where having two different alleles for a gene provides a survival or reproductive advantage compared to having two identical alleles (homozygous)