p020a developmental disabilities mrs. elizabeth keele lecture 2
TRANSCRIPT
P020ADevelopmental Disabilities
Mrs. Elizabeth KeeleLecture 2
Course Content #7
• Describe the 2 types of mental retardation that are determined at the time of conception:–Chromosomal abnormalities–Gene determined disorders
Cells -
• Humans are made up of cells
Cells
• Cell• Nucleus• Chromatin• Chromosomes
What is a chromosome?
• Thread like structures• Inside nucleus of each
cell
What is a chromosome?
• Thread like structures• Composed of – Protein– Deoxyribonucleic acid
(DNA)– Makes up your genes
Somatic Cells / Diploid cells
• 23 Pairs of Chromosomes• Diploid cells contain two
complete sets (2n) of chromosomes
• Total• 46• 1 - Maternal• 1 - Paternal
Sex Cells / Haploid Cells
• Only have 23 chromosomes• Sole representative• sperm / eggs called gametes
Karyotype
2 types of cells:
Somatic cells• Divide through
mitosis
Sex cells• Divide through
meiosis
Course Content #9
• Differentiate between meiosis & mitosis and describe the stages of meiosis and mitosis
Cell division
Mitosis• Equal cell division• Cell duplicates• Divides one time• Result
– 2 - Daughter cell – Identical to mother cell
Meiosis• Reduction division• Divides 2 times• Results
– 4- daughter cells– Haploid cells (1/2 #
chromosomes)
Mitosis
• Interphase–Preparatory –Centrioles
doubles
Mitosis
• Prophase–Chromosomes
double
Mitosis
• Prometaphase–Nucleus dissolves–Polar centrioles–Microtubules
attach
Mitosis
• Metaphase–Chromosome
align
Mitosis
• Anaphase–Chromosomes
separate
Mitosis
• Telophase –Cell division
begins
Mitosis
• Cytokinesis –Two daughter
cells –Identical
• http://www.youtube.com/watch?v=cvlpmmvB_m4
• http://www.youtube.com/watch?v=zGVBAHAsjJM
Cell division
Mitosis• Equal cell division• Cell duplicates• Divides once• Result
– 2 - Daughter cell – Identical to mother cell
Meiosis• Reduction division• 2 divisions• Results
– 4- daughter cells– Haploid cells (1/2 #
chromosomes)
Meiosis
• http://www.youtube.com/watch?v=D1_-mQS_FZ0
• http://www.youtube.com/watch?v=zGVBAHAsjJM
Meiosis
• Sexual reproduction– Form Haploids
• Gamete– Sperm & eggs
• Reduce the number of Chromosomes
Meiosis does two things.
• One diploid cells produces four haploid cells.
Why do we need meiosis?
• Reduce # chromosome• ½
2nd purpose of meiosis
• Genetic diversity• Accomplished
through– independent
assortment– crossing-over
The Stages of Meiosis:
• aka: Reduction Division
Meiosis I : Separates Homologous Chromosomes
• Interphase–Each of the
chromosomes replicate
Prophase I
• Chromosome match up with their homologous pair
• Fasten together (synapsis) – tetrad
• Crossing over can occur. – exchange of segments
Metaphase I
• The chromosomes line up at the equator attached by their centromeres to spindle fibers from centrioles.– Still in homologous pairs
Anaphase I
• spindle move chromosomes toward the poles
Telophase I
• End 1st division• cytoplasm divides – two daughter cells.
Meiosis II : 2nd division
• Proceeds similar to mitosis• THERE IS NO INTERPHASE II !
Prophase II
• Spindle• Move toward equator
Metaphase II
• The chromosomes are positioned on the metaphase plate in a mitosis-like fashion
Anaphase II
• Centromeres separate• Move toward opposite poles– individual chromosomes
Telophase II and Cytokinesis
• Nuclei form at opposite poles of the cell and cytokinesis occurs
• After completion of cytokinesis there are four daughter cells –All are haploid (n)
One Way Meiosis Makes Lots of Different Sex Cells (Gametes) – Independent Assortment
Independent assortment produces 2n distinct gametes, where n = the number of unique chromosomes.
That’s a lot of diversity by this mechanism alone.
In humans, n = 23 and 223 = 6,000,0000.
Meiosis – division error
Chromosome pair
Meiosis error - fertilization
• Often occurs with the 21st pair
• Trisomic zygote
• Downs Syndrome
Course Content #14
• Explain how the presence or absence of a Y chromosome determines the sex of an individual.
23 chromosomes
• 22–Autosomes• Same male to
female• Same loci• Same function
• 1 – Sex chromosome
What is a chromosome?
• In cell nucleus • DNA thread coiled
around proteins – Histones
• Chromosome constriction point – Centromere
How many chromosomes do people have?
• 23 pairs • total of 46.• 22 autosomes
– look the same in both males and females.
• 1 pair sex chromosomes– #23– differ between males and
females.
• Females – XX
• Males – one X and one Y
Can changes in the number of chromosomes affect health and development?
• Normally – 23 pairs of chromosomes– Total 46 chromosomes in
each cell
• Change the # of chromosomes problems with – growth, – development, – function of the body’s
systems.
Chromosomal Abnormalities
Numerical Abnormalities:• Missing a
chromosome from a pair –monosomy
• Two chromosomes• trisomy
Chromosomal AbnormalitiesStructural Abnormalities:
• Deletions: – A portion of the
chromosome is missing or deleted.
• Duplications: – A portion of the
chromosome is duplicated
• Translocations: – A portion of one
chromosome is transferred to another
• Inversions: – A portion of the
chromosome has broken off
Trisomy
• Extra chromosome• Down syndrome– three copies of
chromosome 21– total of 47
chromosomes per cell
Monosomy• Monosomy– loss of one chromosome
in cells, • Turner syndrome is a
condition – Female– only one copy of the X
chromosome – total =45 chromosomes
Course Content #10
• Explain the process by which humans inherit 23 chromosomes from each parent to create a total compliment of 46 chromosomes (23 pairs).
• Meiosis
• Haploid / gamete cells due to reduction have – ? Chromosomes– 23
• Each chromosome is the sole representative of the original 23 pairs
During fertilization…
• sperm + egg = Zygote• 23 + 23 = 46
Course Content #13
• Explain the relationship between the following nitrogenous bases in forming an individuals genetic code:–Adenine– Thymine–Guanine– Cytosine
Course Content #12
• Define and explain the relationship between DNA & RNA
• http://www.youtube.com/watch?v=zwibgNGe4aY
DNA
• Deoxyribonucleic Acid• Carrier genetic code • 4 nitrogenous bases– Adenine– Guanine– Cytosine– Thymine
RNA
• RNA – interprets the
code –Messenger
• DNA • RNA
– Out of nucleus – Cytoplasm– + ribosome (factory)
• Amino Acids (20) • Proteins • Living cells • Tissues • Organs • Living organism
Course Content #11
• Describe the role & function of –Operator genes– Structural genes– Regulator genes
What is a gene?
• Functional unit of heredity.
• Made up of DNA
What is a chromosome
• DNA and histone proteins are packaged into structures called chromosomes.
How many chromosomes do people have?
• 23 pairs• 46 total
What are proteins and what do they do?
• Large, complex molecules
• Made up of smaller units called amino acids
• There are 20 different types of amino acids that can be combined to make a protein.
Can genes be turned on and off in cells?
• Yes• Gene regulation.
types of genes
• Structural gene– Determines the type of
protein to be synthesized
• Operator– Turns protein synthesis on
and off in structural gene
• Regulator– Suppresses or activated
operator and structural genes
What kind of gene mutations are possible?
• Altered DNA sequence
• http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/possiblemutations
What is a gene?
• Most basic unit of heredity
• Particular nucleic acid sequence within DNA molecule
• Carriers of biochemical information to the cell instructing it what kinds of protein it will produce
Course Content #8
• Identify the trait carry elements of heredity
Course Content #16
• Differentiate between autosomal dominant inheritance and autosomal recessive inheritance
Gregor Mendel
• 1822 -1884• Austrian Monk• Experimented with
pea plants• Identified 4 basic
patterns of inheritance
Mendelian Patterns of Inheritance
1. Autosomal Recessive inheritance2. Autosomal Dominant Inheritance3. X-links Recessive inheritance4. X-Links Dominant inheritance
Punnett Squares
• Recessive genes–Blue eyes - b
• Dominant genes–Brown eyes – B
• BB = Brown• Bb = Brown• bb = blue
B BB BB BB
B BB BB
Punnett Squares
• Recessive genes–Blue eyes - b
• Dominant genes–Brown eyes – B
• BB = Brown• Bb = Brown• bb = blue
B bB BB Bb
B BB Bb
Punnett Squares
• Recessive genes–Blue eyes - b
• Dominant genes–Brown eyes – B
• BB = Brown• Bb = Brown• bb = blue
B bB BB Bb
b Bb bb
Punnett Squares
• Recessive genes–Blue eyes - b
• Dominant genes–Brown eyes – B
• BB = Brown• Bb = Brown• bb = blue
B B B BB BB
b BB BB
Autosomal Recessive Inheritance
An autosomal recessive disorder means two copies of an abnormal gene must be present in order for the disease or trait to develop.
-ex: Tay Sachs, PKU, Galactosemia
Autosomal Recessive
Autosomal Recessive
Autosomal Dominant Inheritance
-refers to inheritance of a dominant mutant gene carried on an autosome
-has one good gene, but not enough to make body work or grow correctly
-person will be affected-mutated gene dominates the correct gene copy-ex: Neurofibromatosis, Tuberous Sclerosis
Autosomal Dominant
Autosomal Dominant
X-linked Recessive Inheritance
-refers to inheritance of mutated gene carried on X chromosome
-mutations on X chromosome are most commonly recessive
-since females have two X, can be a carrier, but not generally affected
Ex: Lesch-Nyhan, one type of Fragile X
X-linked Recessive
X-linked Recessive
X-linked Recessive Inheritance(con’t)
-in male offspring: 1:2 chance of being affected; males can’t be carriers
-in females: 1:2 chance of being a carrier, generally unaffected;
X-linked Dominant Inheritance
-refers to inheritance of a mutant gene carried on an X chromosome
-not enough, or no, correct gene product to work or grow properly
-person is affected-mutated gene copy dominates the correct gene
copy -ex: Muscular Dystrophy
X-linked Dominant
X-linked Dominant