Genetics

What are the three chemical components that make up a DNA nucleotide?

• a five-carbon sugar (deoxyribose)

• a phosphate group

• one of four nitrogenous bases

The ________ bases are Adenine (A) and Guanine (G) and have a double-ring structure.

Purine

The _______ are Cytosine (C), Thymine (T), and Uracil (U) and have a have a single-ring structure.

Pyrimidines

 A researcher is comparing a DNA sample to an RNA sample. Which nitrogenous base will they only find in the DNA?

Thymine (T)

 What is the specific chemical difference between the sugar in DNA and the sugar in RNA?

DNA lacks an oxygen atom ("deoxy") on the 2' carbon

In the DNA double helix, Adenine and Thymine are held together by ________ hydrogen bonds., while G-C pairs are held by _____ hydrogen bonds.

Two, Three

 A segment of DNA is "G-C rich." Based on the lecture annotations, what does this imply about its transcription?

Less likely to be transcribed, due to stronger bonds

Describe the structure of the sugar-phosphate backbone and the type of bond involved.

Covalent phosphodiester bonds between the phosphate group of one nucleotide and the sugar of the next.

When synthesizing a new strand, the DNA polymerase always extends in the ________ direction.

5’ to 3’

What is the primary difference between a gene and the genome?

Gene is a segment; Genome is the sum of all genes.

DNA is ________ charged, which is why it is attracted to the positively charged histones.

Negatively

What is a "nucleosome" in the hierarchy of DNA packing?

The basic unit of chromatin, consisting of a segment of DNA wound around a core of histone proteins.

A student sees a dark mass in the nucleus of a cell under a microscope. According to the annotations, what is happening there?

Active Transcription (nucleolus)

______ is fine, filamentous material used for storage.

Chromatin

_______ are the highly condensed form visible only during cell division.

Chromosomes

What are the 3 stages of Transcription?

1. Initiation

2. Elongation

3. Termination

What are "introns" and why must they be removed?

Non-coding "nonsense" segments that must be removed through splicing

 In transcription, the enzyme ________ binds to DNA to assemble mRNA.

RNA polymerase

_______ creates multiple genes from one region by allows enzymes to splice exons together in different ways, producing different functional RNA molecules from the same pre-mRNA.

Alternative Splicing

A patient has a condition where a protein starts with the wrong amino acid. Which "start codon" should have ensured it began with Methionine?

AUG

What codes for the stop codon?

• UAA

• UAG

• UGA

The ________ on a tRNA molecule reads the corresponding codon on the mRNA, ensuring the correct amino acid is delivered to the ribosome.

Anti-codon

What does "redundancy" in the genetic code mean?

Multiple codons for one amino acid

_______ is a regulatory mechanism used to turn genes "off" when their products are not needed.

Methylation

 A hormone stimulates milk production in a mother. Which hormone binds to receptors to activate the gene for the milk protein casein?

Prolactin

List three examples of "terminally differentiated" cells that live in G0 and do not divide.

• Neurons

• Muscle cells

• Osteocytes

During DNA replication, ________ relaxes the supercoiling of the strands.

Topoisomerase

Why is DNA replication called "Semi-Conservative"?

Each new DNA molecule consists of one original "parent" strand and one newly formed "daughter" strand.

________ is the enzyme that links Okazaki fragments together.

DNA ligase

What is the specific error-correction ability of DNA Polymerase III called?

Proofreading capacity

 A cell is in Metaphase. What must happen before it is allowed to split?

All chromosomes are oscillating slightly and perfectly aligned on the midline/cell equator

What occurs during Anaphase of mitosis?

Sister chromatids are pulled apart by centromeres

The physical division of the cytoplasm into two cells is called ________.

Cytokinesis

What are the phases of mitosis?

• Interphase

• Prophase

• Prometaphase

• Metaphase

• Anapahse

• Telophase

• Cytokinesis

_______ is when chromatids cluster on each side of the cell beginning to uncoil from chromatin, while the Rough ER produces new nuclear envelope around each cluster.

Telophase

_________ is when spindle fibers are growing toward chromosomes and attach to the kinetochore on each side of the centromere.

Prometaphase

______________ is when the nucleolus dissapears and chromosomes condense and begin to become visible; formation of the mitotic spindle occurs.

Prophase

__________ is cessation of division upon contact between cells; cancer cells lack this function.

Contact Inhibition

 Meiosis yields ________ haploid daughter cells that are genetically different.

Four (4)

Mitosis yields ______ diploid daughter cells that are genetically identical.

Two (2)

These are the physical sites where homologous chromosomes cross over and swap genetic material.

Chiasmata

A child has a chromosome that is a mixture of their grandmother's and grandfather's DNA. What process caused this?

Crossing-over (Recombination)

 How does Anaphase I of meiosis differ from mitosis?

Sister chromatids are pulled together to poles

An _________ is a chromosomal mutation that involves two breaks in the chromosome, after which the middle region is flipped (rejoined in the opposite orientation).

Inversion

When do cells divide?

• have enough cytoplasm for 2 daughter cells

• replicated their DNA

• have adequate nutrients

• stimulated by growth factor

• neighboring cells die, opening up space

When do cells stop dividing?

• close contact with neighboring cells

• nutrients or growth factor is withdrawn

___________ is a type of mutation caused by losses from translocation, chromosomal crossovers, unequal crossing over, or breaking without rejoining.

Deletion

True or False: Large deletions are more likely to be fatal.

True

________ is a mutation that results from unequal crossing-over between misaligned homologous chromosomes during meiosis, it ma yinvolve a replication of a portion of DNA or an entire chromosome.

Duplication

What is the potential consequence of "Duplications"?

Increased Gene Dosage

A ________ translocation is often undetected because no genetic material is lost.

balanced

Why are all future eggs in a newborn female already in Prophase I?

Primary oocytes start meiosis in utero but are arrested in first prophase until puberty.

What happens to the "extra" chromosomes during oogenesis?

Discarded in polar bodies via degeneration and reabsorption

_______ is a mutation that occurs when chromosomes broken during meiosis and the resulting fragment becomes joined to another chromosome.

Translocation

Define "Allelic Variation" as per the medical genetics terminology.

The presence of different version sequences of a gene at a specific, fixed position on a chromosome.

An ________ trait is one where the gene is located on one of the 22 non-sex chromosomes.

Autosomal

A _________ gene has more than one allele that occupies that gene’s locus within a population.

polymorphic

If an allele is _________, only a single copy of that allele is needed for the trait to be expressed.

dominant

If an allele is ______, both copies of that allele are required for the trait to be expressed.

recessive

________ is the percentage of individuals with a genotype who show the phenotype.

Penetrance

_______ is the degree or severity of a phenotype in individuals.

Expressivity

A patient has a dominant mutation but only half the normal amount of protein is produced, which is not enough for normal function. What is this called?

Haploinsufficiency

________ are rare genetic changes (under 1%), while ________ are common variations (over 1%).

Mutations; Polymorphisms

 What two events during meiosis lead to genetic variation in haploid gametes?

Crossover(Recombination) and Random Segregation

In a pedigree, every affected person has an affected parent, and the trait appears in every generation. What is the inheritance pattern?

Autosomal Dominant

___________ happens to two genes that are on different chromosomes or are more than 50 map units apart on the same chromosome.

independent Assortment

__________ happens when two genes are located closely together on the same chromosome and will deviate from Mendeilan inheritance patterns.

Linkage

____________ is an autosomal dominant disorder that causes 36 or more CAG repeats in the gene and leads to gradual breakdown of the brain.

Huntington’s Disease

_________ is an autosomal recessive disease that is a deletion mutation on chromosome 7q31 and causes thick mucus that is not easily cleared from the lungs.

Cystic Fibrosis

In ________ inheritance, an affected father will pass the trait to all of his daughters but none of his sons.

X-Linked Dominant

Why are X-linked recessive disorders more common in males?

 Only have one X chromosome; if they inherit the mutant allele, they do not have a second X to "mask" it.

_________ is an x-linked condition that causes dysregulatoin of the activity of several genes in the brain. It affects females exclusively and is lethal in males.

Rett Syndrome

A female has a mutation on one X chromosome but shows no symptoms. What mechanism involving Barr-bodies might explain this?

X-inactivation (Lyonization)

 A ________ mutation is a single base change that results in a different amino acid.

Missense

 Why are "Frame-shift mutations" considered so dangerous?

Changes the entire reading frame, resulting in a completely non-functional protein.

________ describes a cell with an abnormal number of chromosomes (e.g., 45 or 47).

Aneuploidy

____________ is when only some people with a certain genetic profile express a trait. For example, variations in the BRCA1 gene can lead to breast cancer in some.

Incomplete penetrance

___________ is when everyone who carries a particular gene variant expresses the trait or develops the disease. For example, brown eyes because every person has some level of brown in their eyes.

Complete penetrance

_________ is an example of an X-linked recessive condition that was thought to be introduced into the royal family by Queen Victoria.

Hemophilia

________ is a deletion of the most terminal portion of the short arm of chromosome 5 (chromosomal mutation).

Cru di Chat syndrome

_________ is a duplication of genetic material on the long (q) arm of chromosome 7 (chromosomal mutation).

7q11.23 duplication syndrome

_________ is an inversion of chromosome 4 causing formation of a ring structure with multiple phenotypes: cleft palate, club feet, testes don’t descend, short life span. (chromosomal mutation)

Four-Ring syndrome

_________ is a translocation mutation in which chromosome 9 and chromosome 22 break and exchange portions, creating an abnormally small chromosome 22 potentially leading to chronic myelogenous leukemia.

The Philadelphia Chromosome

What is the primary cause of aneuploidy?

Non-disjunction; the failure of homologous chromosomes or sister chromatids to separate properly.

Genes that cause chromosome instability are called ________, which encode components of kinetochore, centrosome or mitotic checkpoint.

CIN genes

________ is an extra copy of chromosome 21 that is lethal in 5% of cases and can be classified as standard, mosaic, or translocated.

Down Syndrome (trisomy 21)

_________ is an extra copy of chromosome 18 that causes microcephaly, malformations of the hand and feet, neural tube defects, and malformations of the sex organs; in which survival beyond the neonatal period is uncommon.

Edward syndrome (Trisomy 18)

__________ is an extra copy of chromosome 13 that causes microcephaly, abnormal openings in the skull, malformations of the brain, congenital heart disorders, etc; in which survival beyond the neonatal period is uncommon.

Patau syndrome (Trisomy 13)

________ is an X-chromosome aneuploidy that affects only females and is a complete or partial deletion of one X chromosome leading to a variety of medical issues.

Turner syndrome

______ is an X-chromosome aneuploidy that affects males and is an extra X chromosome that leads to impaired testicular development and lower testosterone.

Klinefelter syndrome

_________ is an X-chromosome aneuploidy that affects females and is the presence of an extra X chromosome that leads to vary symptoms from impaired cognition to genito-urinary deformities.

Triple X syndrome

_______ is a Y-chromosome aneuploidy that affects males and is falsely called the “super-male disease” that causes behavioral/developmental impairment and psychological pathologies.

XYY

________ is an "epigenetic" process where either the maternal or paternal copy of a gene is turned off (usually via methylation).

Genetic Imprinting

A patient has a lack of impulse control when it comes to food. Genetic testing finds a deletion on chromosome 15 inherited from the father. Which imprinting disorder do they have?

Prader-Willi Syndrome

A patient is mentally impaired and extra joyous, especially with loud sounds. Genetic testing finds a deletion on chromosome 15 inherited from the mother. Which imprinting disorder do they have?

Angelman Syndrome

_______ are single base-pair variations, the most common type of genetic variation, found in at least 1% of the population.

Single Nucleotide Polymorphisms (SNPs)

What was the primary purpose of the Human Genome Project?

To determine the sequence of the 3 billion chemical base pairs that make up human DNA.

_________ is an example of an SNP in which there is a nucleotide change on chromosome 11.

Sickle Cell Anemia

A ________ test is used to examine the number and structure of chromosomes and detect gross chromosomal abnormalities like trisomies or large translocations.

Cytogenetic (Karyotyping)

What does FISH (Fluorescent In Situ Hybridization) detect?

It uses fluorescent probes to visualize specific DNA sequences on chromosomes