SBI3U - Genetics

Non-disjunction

* The failure of homologous chromosomes to move to opposite poles of the cell during meiosis;
* results in an abnormal number of chromosomes in the daughter cells
* Trisomy (24)
* Monosomy (23)

Autosomes

Chromosome pair #1-22

Sex Chromosomes

* Chromosome pair 23
* determines gender
* female (XX)
* Male (XY)

karyotype

The chromosomes of an individual that have been sorted and arranged according to size and shape

XO (Female)

Turner Syndrome 

* Sterile, short/stockier build
* Most XO fetuses usually die.
* **Disorders of Sex Chromosome Non-disjunction**

Triple X Syndrome 

XXX

(Female)

* 1/1000 female births
* poorly diagnosed

XXY (Male)

Klinefelter Syndrome

* Can exhibit female characteristics,
* **Disorders of Sex Chromosome Non-disjunction**

Trisomy 21

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Down syndrome

* round face, short height
* range of intellectual abilities
* **Disorders of Autosomal Non-disjunction**

Trisomy 13

Patau Syndrome

* serious developmental problems
* live several months (sometimes yrs)
* **Disorders of Autosomal Non-disjunction**

Trisomy 18

Edwards Syndrome

* many organ system failures
* most die before birth


* **Disorders of Autosomal Non-disjunction**

Why does primary nondisjunction occurs more often in women than men?

* because all the eggs a woman will produce have begun their development (to Prophase I) by the time she is born. 


* Therefore, a much greater chance exists for problems to occur in the gametes of women than men.

Mendel’s Law of Segregation

* Gametes only carry one allele for a gene

Law of Independent Assortment

* Different characteristics are inherited independently from one another

Pedigree

* a diagram of of an individual's ancestors used in human genetics
* to analyze the Mendelian inheritance of a certain trait;
* also used for selective breeding of plants and animals.

GAMETOGENESIS

* The formation of sex cells in meiosis

Describe OOGENESIS

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* Egg cell formation
* The CYTOPLASM does NOT divide equally
* Daughter cells with less cytoplasm called POLAR BODIES
* Polar bodies will DIE therefore final product is A SINGLE OVUM (EGG CELL)

Describe SPERMATOGENESIS

* Sperm cell formation is called
* Cytoplasm is divided equally
* Forms FOUR equal sized SPERM CELLS
* Each sperm cell is SMALL AND STREAMLINED in size

**Incomplete Dominance**

Occurs when two different alleles control a characteristic, but neither is dominant so both are expressed or blended in the phenotype.

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**Codominance**

both allele products appear in the offspring at the same time.

Sex linked inherited traits

Hemophilia, color blindness, male pattern balding,, muscular dystrophy

hemophilia:

* bleeding disorder in which the blood does not clot properly.


* This can lead to spontaneous bleeding as well as bleeding following injuries or surgery.

Muscular dystrophy:

* Over time, muscle weakness decreases mobility, making everyday tasks difficult.

Interphase (Mitosis)

* grows
* DNA replicates
* The cell performs its daily functions

Prophase (Mitosis)

* Spindle fibers form
* Nuclear membrane begins to dissolve
* Centrioles begin to move to opposite sides

Metaphase (Mitosis)

* The spindle fibbers move the chromosomes to the equator

Anaphase (Mitosis)

* spindle fibbers shorten and contract pulling apart chromosomes and pulling each sister chromatid

telophase/cytokinesis (Mitosis)

telophase:

* spindle fibre’s disappear
* nuclear membrane begins to reform
* the cell begins to divide

cytokinesis:

* the cell separates into two identical *daughter* cells
* the cytoplasm seperate’s

Prophase 1 (Meiosis)

* in a process called synapsis, chromosomes pair up & bind to form homologous chromosomes forming a tetrad
* In a process called crossing over chromatids from homologous homologous chromosomes exchange allies to create genetic verity
* nuclear membrane dissolves
* spindle fibers form

Metaphase 1 (meiosis)

* tetrads line up at the equator attached to the spindle fibers
* random assortment is when homologous pairs are randomly orientated to face opposite poles

Describe this photo Meiosis

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Describe Alkaptonuria

* the accumulation of alkapton in the body
* kidney stones cause damage to cartilage
* recessive allele

 Describe (cystic fibrosis)

* body creates thick sticky mucus that clogs the lungs
* blocks the release of enzymes from the pancreas
* recessive allele

Describe PKU (Phenylketonuria)

* Accumulation of phenylalanine
* poor mental development and growth
* weak tooth enamel
* recessive allele

Tay Sachs Disease.

* nerve cells in the brain are effected


* deuteriation of muscles and physical abilities

Name all recessive autosomal diseases (5)

* Tay Sachs Disease
* PKU (Phenylketonuria)
*  Describe (cystic fibrosis)
* Alkaptonuria
* Albinism

Progeria

* genetic disorder that causes accelerated aging in children. It is caused by a mutation
* dominate allele

Huntington’s

* degeneration of nervous system that causes loss in muscular control and cognitive abilities
* dominate allele

Hypercholesterolemia

* high levels of cholesterol accumulation in the blood
* dominate allele

Name all dominate autosomal diseases (3)

* Progeria
* Huntington’s
* Hypercholesterolemia

What does DNA stand for

Deoxyribo==nucleic== %%acid%%

Who is Hammering and what did he figure out?

* In 1930 Hammering found out that genetic information is found in the nucleus
* Before that scientist had no idea DNA held genetic information

What happened in 1952

* Hershey and chase experiment confirmed that DNA carried genetic information

What is the basic unit of Dna

* Nucleotide

What are nucleotides made up of

* Sugar (deoxyribose)
* nitrogenous base
* Phosphate

What are the 4 different types of bases

* Adenine (A)
* Thymine (T)
* Cytosine (C)
* Guanine (G)

A+T (%%**A**%%pple grow on %%**T**%%rees)

C+G (%%**C**%%ars go in %%**G**%%rudges)

Describe this photo

What are mutations?

* Changes to the gene or even chromosome.
* Can be helpful, harmful or have no impact depending on the location of the mutation and the impacts it could have

Describe the three types of point mutations.

* %%substitution%% - one nucleotide is substituted for another
* %%insertion%% - an extra nucleotide(s) is inserted into a sequence of nucleotides
* %%deletion%% - a nucleotide(s) is removed from a sequence of nucleotides

How does DNA make a protein

* the information in the sequence of DNA nucleotides is read by ribosomes that make proteins.

Which do you think is more devastating, a point mutation or a chromosomal mutation?

* chromosomal mutation because it impacts 100s or 1000s of genes whereas a point mutation is an error in one gene.

Compare animal mitosis and plant mitosis

Animal:

* have centrioles to organize spindle fibers
* forms a cleavage furrow when becoming two daughter cells

Plant:

* no centrioles so microtubles organize the spindle fibers
* forms a cell plate when separating into two daughters cells

mitosis

* body cells dividing to two identical daughter cells

meiosis

* production of gametes (sex cells) that are genetically unique

gamets

* haploid

reproductive cells (sperm/egg)

* haploid 1n (one set of chromosomes)

diploid

carries 2 sets of chromosomes (parents)

* 2n