HSS 2305 U-1

What does it mean to say that genetics is a dynamic science?

new findings all the time

Who is the "father of modern genetics"?

Gregor Mendel

Define "genes"

chemical factors that determine characteristics

What does it mean if something is homozygous?

pure breds with two identical genes

What does it mean if something is heterozygous?

hybrids (don't have identical genes)

Define "alleles"

genes responsible for contrasting characteristics (ex. short or tall)

What does the law of uniformity say?

when two homozygotes with different alleles are crossed all the offspring are identical and heterozygous

What does the law of segregation say?

each person has two genes for particular characteristics but only one gene can be transmitted at a time

What does the law of independent assortment say?

members of different gene pairs segregate to offspring independently of one another

What is the rare exception to the law of segregation?

when two allelic genes fail to seperate bc of chromosome nondisjunction at the first meiotic division.

What are the 3 main principles derived from Mendel's plant experiments?

law of uniformity
law of segregation
law of independent assortment

What is biochemical genetics?

the study of the cause of many specific heritable diseases

What is the role of the nucleus?

control centre of the cell

What is the role of DNA?

provides instructions for protein synthesis

What is the role of peroxisomes?

detox center

What is the role of lysosomes?

digest unwanted substances (autophagy)

What is the role of the smooth endoplasmic reticulum?

produces steroid hormones, lipids etc

What is the role of the rough endoplasmic reticulum?

produces proteins

What is the role of the golgi apparatus?

modifies products from RER

What is the role of ribosomes?

synthesize proteins from mRNA

What is the role of the mitochondria?

generates most of the cells energy (ATP), cell resp

True or False: Cells with high energy requirements have more mitochondria

true

What is the role of the nucleolus?

site of ribosome sub-unit assembly

What is the role of centrioles?

necessary for karyokinesis (nuclear division)

What is the human genome?

the entire set of chromosomes of the human organism

What are the two types of DNA?

mitochondrial and nuclear DNA

What are the differences between mitochondrial DNA and nuclear DNA?

mtDNA is circular, has multiple copies is inherited ONLY from the mother while nuDNA is linear, has two copies and is inherited from both parents

Which type of DNA is important for ancestry studies and forensic investigations?

mitochondrial DNA

What are the 4 nitrogenous bases DNA is composed of?

adenine, guanine, cytosine, thymine

DNA + _______ = chromatin

proteins

What is a karyotype?

an image of stained chromosomes

During RNA processing what happens to introns and exons?

introns are removed and exons are spliced together

What is the role of the promoter region?

regulates gene transcription

Is DNA or RNA single stranded?

RNA

What are the basic mechanisms of transcription?

RNA polymerase binds to promoter region, RNA polymerase reads the unwound DNA and builds the mRNA molecule, termination occurs and mRNA strand is complete

What happens to mRNA before it leaves the nucleus?

splicing, capping and polyadenylation

What are the basic mechanisms of translation?

mRNA is read in groups of 3 (codon) and copied at the ribosomes to make protein

What are gene mutations?

permanent alterations in the DNA sequence

What are somatic mutations?

mutations in normal body cells that cause adult onset disease but are NOT transmitted to offspring

What are gamete mutations?

mutations in the sex cells that can be transmitted to future generations (won't it person can't have kids or doesn't make it to that age)

What is a deletion?

a type of mutation that removes a piece of DNA

Are somatic (body) cells diploid or haploid?

diploid

Are gametes (sex cells) diploid or haploid?

haploid

What are the 2 phases of the cell cycle?

interphase and M phase

What are the 3 stages of interphase?

G1 phase, S phase, G2 phase

What happens during G1 phase?

cell grows and prepares for DNA replication

What happens during S phase?

DNA is replictated

What happens during G2 phase?

cell finishes growing and prepares for cell division

What are the 2 stages of M phase?

mitosis, cytokinesis

What happens during mitosis?

nuclear division (DNA is separated into two identical nuclei)

What happens during cytokinesis?

the cell splits into two

Why is DNA replication deemed semi-conservative?

because only one strand is newly synthesized

The synthesis of DNA strands occurs in what direction?

5'-3'

What are the 4 stages of mitosis?

prophase, metaphase, anaphase, telophase

What happens during prophase in mitosis?

chromosomes condense, nuclear membrane and nucleus dissolve, microtubule spindles form

What happens during metaphase in mitosis?

microtubule spindles connect to centromere of each chromosome and depolymerize causing chromosomes to align along the centre

What happens during anaphase in mitosis?

sister chromatids separate and move to opposite poles

What happens during telophase in mitosis?

spindle fibres dissolve, chromosomes decondense, nuclear membrane reforms, cell splits into two (cytokinesis)

What is supercoiling?

tightly winding and condensing DNA into chromosomes

What does a metacentric chromosome look like?

centromere is in the middle of the chromosome

What does a submetacentric chromosome look like?

centromere is closer to the top of the chromosome

What does a acrocentric chromosome look like?

looks like an alien

What does a dysfunctional tripolar miotic figure indicate?

neoplasia (cancer)

What are the steps of DNA replication?

DNA helicase unzips DNA strands, DNA polymerase adds the complimenting nucleotide base and forms a replication fork

How are the okazaki fragments in the lagging strand joined together?

DNA ligase

What happens in meiosis I?

homologous pair of replicated chromosomes are separated

What happens in meiosis II?

sister chromatids are separated

What is the growth phase in-between meiosis I and II called?

interkinesis

What happens during prophase I in meiosis I?

cross over, chromosomes condense, nuclear membrane disappears

What happens during metaphase I in meiosis I?

spindles connect to centromeres of tetrads and line them up in the middle

What happens during anaphase I in meiosis I?

tetrad is split and homologous chromosomes move to opposite poles

What happens during telophase I in meiosis I?

cell divides to form two haploid cells

What happens during prophase II in meiosis II?

chromosomes condense, nuclear membrane disappears

What happens during metaphase II in meiosis II?

spindle fibres attach to centromeres and align chromosomes along cell equator

What happens during anaphase II in meiosis II?

sister chromatids are separated and move to opposite poles

What happens during telophase II in meiosis II?

cell divides to form 4 haploid cells

What two events explain why no person is genetically identical?

random assortment, crossing over

What is random assortment?

the random separation of chromosomes that results in random gamete order

During what phase of meiosis does random assortment occur?

anaphase

Where does crossing over occur?

at the chiasmata

What is a chiasmata?

the point that hold homologous chromosomes together

What is non-invasive prenatal testing (NIPT) used for?

to detect chromosomal abnormalities in a developing fetus

What is aneuploidy?

an extra or missing chromosome

What is euploidy?

when a cell has 46 chromosomes

What are the two types of aneuploidy?

monosomy, trisomy

What is monosomy?

when an organism only has one copy of a chromosome instead of two copies (45 chromosomes)

What is trisomy?

when an organism has a third copy of a chromosome instead of two copies (47 chromosomes)

What causes disorders of chromosome numbers?

non disjunction

What is non disjunction?

when pairs of homologous chromosomes or sister chromatids fail to separate durig meiosis I or II

What is an example of a monosomy disorder?

turner syndrome

What are examples of trisomy disorders?

kleinfelter syndrome (XXY), trisomy 21

What are common physical features of down syndrome?

flattened face, almond shaped eyes that slant up, flat nose

Why must trisomy 21 diagnosed through CVS always be confirmed by a postnatal specimen?

because the placenta might contain mosaic cell lines not present in the fetus

What is the most frequently occurring chromosomal congenital anomaly in Canada?

down syndrome

What are the 3 types of down syndrome?

trisomy 21, translocation down syndrome, mosaic down syndrome

What is translocation down syndrome?

down syndrome that occurs when an extra part or a whole extra chromosome 21 is present but is attached to a different chromosome rather than being separate

What is mosaic down syndrome?

down syndrome that occurs when some cells have 3 copies of chromosome 21 but other cells have 2 copies

What are block mutations?

changes to segments of a chromosome that lead to large changes in DNA

What are duplication mutations?

part of the chromosome is copied

What are inversion mutations?

segment of a chromosome is removed and replaced within the chromosome in reverse order