MT6315 L4 CHROMOSOMES Flashcards
carried traits from one generation to the next
Mendelian “factors”
Who recognized and explored the fibrous network within the nucleus? And what are these networks?
Walther Flemming and it is chromatin or “stainable material”
center of the cell where genetic material is formed
nucleus
What did Walther Flemming observe in cell division stages?
observed cells in various stages of division and recognized that chromosomal movement during mitosis offered a mechanism for the precise distribution of nuclear material during cell division
What did Theodor Boveri discover?
first evidence that germ cell chromosomes imparted continuity between generations
observed cells during meiosis
What was Boveri’s profession?
Embryologist
What did Boveri focus on?
cytoplasmic changes to see possible changes in the offspring
What kind of embryos did Boveri work with?
Ascaris embryos that first depicted meiosis
What did Walter Sutton discover?
described the configurations of individual chromosomes in cells at various stages of meiosis (testes of Brachystola magna) on grasshoppers
Who confirmed and expanded upon Boveri’s observations?
Walter Sutton
Sutton and Boveri’s experiments provided physical basis for?
physical basis of the Mendelian law of heredity – developed the “Chromosomal Theory of Inheritance
Boveri hoped that his experiments would also help to distinguish the roles of the______ and ________ in _______.
nucleus and the cytoplasm; embryogenesis.
T or F: Boveri was particularly interested in how offspring are shaped by the attributes of their parents.
T
Who experimentally demonstrated Chromosomal Theory of Inheritance using Drosophila melanogaster and pioneered “Fly Room” experiments?
Thomas Hunt Morgan
Who helped establish the chromosomal basis of heredity and sex?
Calvin Bridges
What else did Calvin Bridges discover?
nondisjunction caused chromosomes, under some circumstances, to fail to separate when forming sperm and egg cells.
nondisjunction caused sperm or egg cells to contain abnormal amounts of chromosomes, and the offspring produced by the sperm or eggs would display traits that they would typically not have.
Chromosomes are also called?
“colored bodies” or thread-like structures
Chroma=color
Soma=body
Chromosomes are made of?
a protein and a single molecule of has DNA, and some minute RNA
What do chromosomes do?
Enable transmission of genetic information from one generation to the next
What do chromosomes do in the context of mitosis?
Ensure daughter cell retains complete genetic complement
What do chromosomes do in the context of meiosis?
Enable each mature ovum and sperm to contain a unique single set of parental genes
Why is having a unique set of genes important in meiosis?
genetic recombination protects us from diseases and create new genetically different species from parents
How many chromosomes in the human?
44 autosomes
2 sex chromosomes
Extra-chromosomal DNA
̶ Other DNA materials found in the mitochondria
How many meters of DNA in a chromosome?
about 2m
How many base pairs per set of chromosomes?
about 3 billion
How many genes code for proteins that perform most life structures?
20,000-25,000
Replicated chromatids condensed chromosome with sister chromatid
Metaphase chromosome
What is the protein that links DNA together?
H1 Histones
What composes the nucleosome?
8 histone globus and 147 nucleotide pairs, 1 peripheral protein (H1 Histone)
Telomeres resemble?
aglets of shoelace
What is the technique that cytogeneticists employ in order to produce a banding pattern in individual chromosome?
G-banding
Cytogeneticists make use of diagrams referred to as __________ to determine the ______ and ______ of chromosomes.
chromosome ideograms
relative sizes and the banding patterns
What are the other types of banding techniques?
- Reverse (R-) banding,
- Constitutive heterochromatin (C-) banding,
- Quinacrine (Q-) banding,
- Nucleolar Organizer Region (NOR-) banding, and telomeric R (T-) banding.
Giemsa stain is a compound of? And utilizes what?
methylene blue-eosin and methylene blue
utilizes acetic acid fixation, air drying, denaturing chromosomes mildly with proteolytic enzymes, salts, heat, detergents, or urea, and finally giemsa stain.
Chromosome bands appear similar to those ________ by _______
fluorochromed by Q-banding stain
Regions in the chromosome that stain _____with G-banding tend to be more transcriptionally active, euchromatic, and rich with guanine and cytosine.
rather lightly
______ also makes use of Giemsa stain that binds to ______.
C-banding ; constitutive heterochromatin.
Two identical strands which are the result of DNA replication
Chromatids
What is the centromere?
Central region
Primary constriction where sister chromatids are linked
Consists of several hundred kilobases of repetitive DNA
Responsible for chromosome movement at cell division
Centromere divides the chromosome into?
▪ Short arm: designated as p (petite)
▪ Long arm: designated as q (queues or “g” = grande)
What are alphoid chromosomes?
Centromeric regions of primate chromosomes are dominated by alphoid (alpha satellite) DNA, a family of tandemly repeated nontranscribed sequences
Satellite DNA belongs to which region of genome?
the non-coding region
Tandem repeats occur when?
a pattern of 2 or more nucleotides are repeated adjacent to one another.
Satellite DNA is concentrated where?
near the centromere and telomere regions of chromosomes and forms a large part of heterochromatin.
How many repeating units in alpha satellite?
171
How many repeating units in beta satellite?
68
How many repeating units in micro satellite?
2-10
How many repeating units in mini satellite?
10-100
Organelle located at the centromere region
Kinetochore
Kinetochore is responsible for?
Microtubule Organizing Center
Spindle formation
Chromosome types based on number of centromeres?
Monocentric
Acentric
Dicentric
genetically unstable because they cannot be maneuvered properly during cell division and are usually lost
Acentric
genetically unstable because it is not transmitted in a predictable fashion
Dicentric
Types of chromosomes based on centromere position?
Metacentric
Sub-metacentric
Acrocentric
Telocentric
severely off-set from centre, leading to much shorter p arm
Acrocentric
centromere off-centre, leading to shorter p arm relative to q arm
Submetacentric
chromosome is X shape
Metacentric
centromere found at end of chromosome, meaning no p arm exists
Telocentric
13 - 15, 21, 22, Y
Acrocentric
2, 4 - 12, 17, 18, X
Submetacentric
Not found in humans
Telocentric
1st, 3rd, 16th, 19th and 20th
Metacentric
5 pairs in humans
Metacentric, Acrocentric
Arm ratio - 1.0-1.6/1.7
Metacentric
Arm ratio - 3.0
Submetacentric
Arm ratio - 3.1-6.9
Subtelomeric
Arm ratio - 7.0
Acrocentric
Telomere contains repeated of what sequence?
hexameric sequence ‘TTAGGG’
What maintains the structure and form of the telomeres?
Lariat model
region of repetitive nucleotide sequences associated with specialized proteins
Telomeres
Telomere Functions in preserving chromosome stability?
Preventing abnormal end-to-end fusion
Protecting the ends of chromosomes from degradation
Ensuring complete DNA replication
Having a role in chromosome pairing during meiosis
During early meiosis, telomeres play the distinctive function of ?
anchoring chromosomes to the inner nuclear membrane.
As a consequence of the nuclear membrane polarization, what happens to the telomeres?
telomeres cluster together into a bouquet configuration, which facilitates pairing and recombination of the homologous chromosomes
Individuals with______ telomeres have been reported to have a longer subsequent lifespan in some studies of vertebrate species
longer
What is the end of replication problem?
the ends of linear DNA cannot be replicated completely during lagging strand DNA synthesis, leading to progressive shortening of the telomeric DNA during each round of DNA synthesis, reducing telomeric protective capacity
accepted for explaining telomere attrition during cell proliferation
progressive shortening of telomeres that lowers if protective capability
What is telomerase?
ribonucleoprotein enzyme which carries out the task of adding repetitive nucleotide sequences to the ends of the DNA.
What does telomerase do?
Telomerase “replenishes” the telomere “cap” and requires no ATP
Where is telomerase active in eukaryotes?
germ cells, some types of stem cells such as embryonic stem cells, and certain white blood cells.
T or F: Telomerase cannot be reactivated.
F; it can be, reverting the telomere back into the embryonic state by somatic cell nuclear transfer
The steady shortening of telomeres with each replication in somatic (body) cells may have a role in?
senescence and in the prevention of cancer
In vitro studies have shown that telomeres accumulate damage due to _____ .
oxidative stress
In Telomere damage, oxidative stress-mediated DNA damage has a major influence on_____.
telomere shortening in vivo.
The phenomenon of limited cellular division was first observed by? Which is now called?
Leonard Hayflick, and is now referred to as the Hayflick limit.
Additional to the Hayflick model, significant discoveries were subsequently made by?
a group of scientists organized at Geron Corporation by Geron’s founder Michael D. West, that tied telomere shortening with the Hayflick limit.
Theodor Boveri developed the chromosomal theory of inheritance and the idea of?
Chromosomal individuality
Who are the pioneers for the discovery of sex chromosomes and association between specific genes and specific chromosomes?
Thomas Hunt Morgan
Calvin Bridges
T or F: Calvin Bridges also used Drosophila to prove his experiments in nondisjunction
T
What is an example of a mitochondrial sickness?
MELAS (Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes)
What protects the end of the chromosomes?
Telomeres
What wraps around the histone octamer?
DNA double helix
When nucleosomes bind together, what forms?
A 3-D zigzag structure with histone H1 and other DNA-binding proteins
Condensed nucleosomes form what structure? What binds these together?
Solenoid structure, bound together by bent Linker DNA
Cytogeneticists employ staining techniques to determine the pattern of?
Characteristic pattern of light and dark bands
Chromosomal shorthand for DiGeorge Syndrome?
del22q 11.2
Chromosomal shorthand for Cystic fibrosis transmembrane conductance regulator (CF)?
7q 31.2
5-300 base pairs long and are part of the high evolving eukaryotic genome
Satellite DNA
Location of beta-satellites?
In the pericentric region
What kind of satellite DNA is dispersed all throughout the chromosome?
Microsatellite
What Satellite DNA is found in the telomeric region?
Minisatellite
The kinetochore contains how many regions? What are these regions and their functions?
Inner kinetochore - tightly associated with the centromere
Outer kinetochore - interacts with microtubules
Chromosome type that is a broken fragment left after breaking off from a chromosomal fragile site
Acentric
Chromosomal type that is left in the metaphase plate because of the lack of kinetochores
Acentric
Chromosome type that fused chromosomes in cases precipitated by conditions like Robertsonian translocation
Dicentric
What are the metacentric chromosomes?
1,3,16,19,20
What are the submetacentric chromosomes?
2,4-12,17,18,X
What are the Acrocentric chromosomes?
13-15,21,22,Y
In Acrocentric chromosomes, the p arm is very short, thus they are considered as?
satellite regions
T or F: Loss of the satellite regions in the acrocentric chromosomes will still lead to genetic aberrations
T
During anaphase, what is the shape of metacentric chromosomes?
V shaped
During anaphase, what is the shape of submetacentric chromosomes?
J shaped
During anaphase, what is the shape of acrocentric chromosomes?
I shaped
Where are telocentric chromosomes usually found?
In Oxalis (Shamrock)
Who created the chromosome type based on arms ratio?
Levan et al
What is another name for arm ratio in chromosomes? Hint: It’s an equation
L/S
What protein is responsible for the packaging of DNA in the cell nucleus? Why is this necessary?
Histones (H1 histones, histone octamers)
This is important to make DNA be able to fit into the nucleus, needs to be tightly packed
What is the role of telomeres in cancer development?
As a cell begins to become cancerous, it divides more often, and its telomeres become very short. If its telomeres get too short, the cell may die. Often times, these cells escape death by making more telomerase enzyme, which prevents the telomeres from getting even shorter.
