HBIO 370 - Exam 1 - Basis of Inheritance

Genetics is the branch of science concerned with

genes, heredity, & variation in living organisms

Where is genetic information stored?

Nucleus in DNA

How many strands are antiparallel?

two strands of DNA

How many strands are bound by hydrogen bonds?

two strands of DNA

G & C make how many hydrogen bonds… while T & A make _____ bonds

three, two

Purines consist of:

adenine and guanine

Pyrimidines consist of:

Cytosine, Uracil, Thymine

Each nucleotide consists of:

a sugar, phosphate, and a base

DNA & Histones are packed to form…

Nucleosomes

Nucleosomes are compacted in a helical shape called

Solenoid

Solenoid

assembled to form a loop and with a protein scaffold they form the Chromosome

True or false… Telocentric chromosomes only exist in humans

False

What are acrocentric chromosomes?

Chromosomes with the centromere located near one end, resulting in a long arm and a short arm.

Describe a submetacentric chromosome

A chromosome with the centromere located slightly off-center, creating two arms of unequal length.

What is a metacentric chromosome?

A chromosome with the centromere located in the middle, resulting in two arms of equal length.

Telomerase enzyme replaces the telomeres lost with…

DNA replication

Size of centromeres

0.3-5 Mb, for cell division

Haploid genotype

23 chromosomes, in gametes

Diploid genotype

46 chromosomes, somatic cells

What does the mitotic phase consist of?

mitosis and cytokinesis

Interphase is…

cell growth, copying of chromosomes in preparation for cell division including G1, S, and G2

G1 phase

the first phase of interphase where the cell grows and synthesizes proteins.

S phase

the phase of interphase where DNA is replicated, resulting in the duplication of chromosomes.

G2 phase

the second gap phase of interphase following DNA replication, where the cell continues to grow and prepares for mitosis.

Mitosis

Process of cell division (somatic)

In mitosis,

1 mother cell gives rise to 2 daughter cells

During mitosis each chromosome is separated
into the

two sister chromatids.

two sister chromatids replicate during…

the S phase of interphase.

Stages of Mitosis

Prophase, Metaphase, Anaphase, Telophase

What occurs during cytokinesis?

cell divides, 2 daughter cells form

What happens during telophase?

Mitotic spindle disappears, nuclear envelope begins to reform, cell division begins

Anaphase

mitotic spindle pulls sister chromatids to opposite poles

Cells are blocked in ______ to retrieve chromosomes

metaphase

G banding method

treatment with trypsin, and stained with dyes

Heterochromatin

dark, condensed DNA, not expressed

Euchromatin

light bands, less condensed, actively expressed

Autosomes

22 pairs

What does the CFTR location map gene 7q31.2 mean?

chromosome 7

q arm (long)

band 3

sub-band 1

sub-sub-band 2

Aneuploidy

loss or gain of 1 chromosome

Monosomy

missing one chromosome

Trisomy

one extra chromosome

Tetrasomy

not in humans

Polyploidy

gain of 1 complete haploid complement

Polyploidy can result in

Miscarriage

No cytokinesis

2 spermatozoa, fertilize 1 oocyte

Why don’t women suffer from having 2 X chromosomes?

Due to X inactivation, one is silent, the other is expressed (lyionization)

Inactivation is the condensation of: one X chromosome to form the…

Barr Body

Barr Body is:

an inactivated X chromosome that exists to complement the active form

Trisomy

21, 18, 13 (XXX, XXY, XYY)

Trisomy 13

Patau Syndrome

Trisomy 18

Edward’s Syndrome

Triple X syndrome

47, XXX

Klinefelter syndrome

47, XXY

Jacob Syndrome

47, XYY

S phase: DNA replication

Sister chromatids identical, replicated during synthesis

One chromatid is used as a template

New DNA molecules are made up of one of the ________ plus
a new half.

As a result, DNA replication is
called ______

original parental strands

semi-conservative

DNA Polymerase synthesizes DNA using a template and works in a ____________

5’ to 3’ direction

Each bubble on chromosome allows for:

replication for a leading strand and a lagging strand

Okazaki fragments are synthesized in the…

lagging strand

DNA polymerase requires ____ to function

primers

primers

short RNA sequences (~20 nu) from which the DNA
poly can start to amplify DNA

exonucleases

they can degrade the RNA primers they find ahead and replace them
with DNA, they cannot seal the nicks

Initiation

Proteins bind to DNA, open up double helix, and prepare DNA

Elongation

Proteins connect the correct sequence of nucleotides into a continuous strand of DNA

Termination

Proteins release the replication complex to cut the DNA to avoid
tension damage caused by overwinding to stabilize SS DNA

Helices

Separates 2 strands

Primase

Synthesizes RNA primers

Single strand binding proteins

Prevents reannealing of single strands

DNA ligase

Seals nicks in DNA

DNA polymerase

Synthesizes DNA, polymerases in eukaryotes also function as an exonuclease

Telomerase

enzymes that restore telomere length to avoid DNA loss (only in certain cells)

Topoisomerase

Prevents torsion/breaks

Pseudogenes

not expressed, 𝛹, resemble coding genes, produced by gene duplication/inactivating mutations

Tandem

they are clustered together and oriented in
the same direction

Microsatellites

2-4 bps 10-30 repeats

Rarely on coding genes, can cause disease

Minisatellites

telomeres, hypervariable minisatellite

Satellites

several hundreds bps clustered around centromeres

transposable element

a DNA sequence that can change its position within a genome

Transposons

create or reverse mutations and
alter the genome size, thus creating genetic
diversity

TE can make up to _____ of human genome

45%

How do TE work?

DNA Transposons, Retrotransposons

SINEs Short Interspersed Nuclear Elements

~300 bp in 1 millin copies (Alu)

10% of genome

Originated from transposons - have short sequences recognized by tranposases

All are retrotransposons

LINEs Long Interspersed Nuclear Elements

17% of human genome

Line-1 in 6000 bp in > 100,000 copies

Line 1 is a Retrotransposon

Coded for transposes enzyme

Alu elements can cause disease by…

insertion, homologous recombination

Mitochondria contain a

16.6 kb circular ad double-stranded genome

DNA directs the production of proteins
via an intermediate molecule of DNA

F, RNA

exons

coding regions

introns

non-coding regions that are
removed during the splicing process

Capping is the addition of a 5’ cap, which facilitates…

mRNA export and protects the molecule

200 adenines are added to the 5’ end to facilitate
export

3’ end, F

Translation takes place in the…

cytoplasm by ribosomes, made of rRNA and proteins

Ribosomes read mRNA and use tRNA to produce a string of amino acids by ___________ on the mRNA with nucleotides on the tRNA

pairing up nucleotides

3 nu on the tRNA make an ______

3 nu on the mRNA make a ________

Each tRNA also binds one of ______

anticodon, codon, 20 AAs

Gametogenesis

oogenesis and spermatogenesis

Crossing over

occurs when homologous chromosomes line
up during meiosis I.

Meiosis is arrested in _____ (diplotene) at birth

prophase I

With ovulation, meiosis continues and is arrested at _________

metaphase II

Non-disjunction

he failure of homologous chromosomes or sister
chromatids to separate properly during cell division

There is two globin chains on alpha 1 and alpha 2

T

The coding strand (DNA) - TTC 

Find the Template:

mRNA (Codon):

Anticodon tRNA:

AAG, UUC, AAG

Synaptonemal complex

keeps homologous chromosomes together until pregnancy