Bellwork: Wed. Dec. 6, 2017 Review: 1. 2 of our 46 human chromosomes are known as_____________________  because they determine an individual's sex. Females have two copies of an X chromosome. Males have one X chromosome and one Y chromosome. 2. The other ____ chromosomes are known as autosomes. 3. How is the sex of an organism determined?

Beetle Karyotype Lab How Can Karyotype Analysis Detect Genetic Disorders

Then scientists cut out the chromosomes from the photographs and group them together in pairs.

Human Karyotype A picture of chromosomes arranged in allele pairs. Karyotypes are often used to determine whether or not an unborn fetus has a genetic abnormality or not These human chromosomes have been cut out of a photograph and arranged to form a karyotype. Photo credit: ©CNRI/Science Photo Library/Photo Researchers, Inc. karyotyping activity

Deletion occurs when a piece of a chromosome breaks off, resulting in the loss of some genes

Duplication An extra copy of all or part of a chromosome

Nondisjunction The addition or loss of an entire chromosome. This occurs when homologous pairs (tetrads) do not separate properly during Anaphase I of Meiosis.  This failure to separate chromosomes properly leads to a condition in which the offspring has an abnormal number of chromosomes.  The condition of having an extra chromosome in one of it pairs is called trisomy (a human with trisomy would have 47 chromosomes instead of 46).  When an organism is missing one of its chromosomes, the condition is called monosomy (a human would have 45 chromosomes) .  

Bellwork: Dec. 7, 2017 Chromosome error Disorder D is the Normal karyotype for a species of butterfly. Use the chart and the karyotypes of Butterflies A, B, and C to describe the chromosome error and and disorder of each: Butterfly A Chromosome Error Disorder Trisomy of pair 3 Short antennae Duplication on pair 1 Extra wings Deletion on pair 2 Lack of blue pigmentation D Normal Female Butterfly B Chromosome error Disorder Butterfly C Butterfly A: Butterfly B: Butterfly C:

Insertion (addition) happens when a piece of  a chromosome breaks off and attaches to a homologous pair (thereby getting a repeating piece)

Inversion   occurs when a piece of a chromosome is rotated, which reverses the order of genes in a the chromosome

Translocation is the transfer of a part of a chromosome to a nonhomologous chromosome

Gene Mutations: Point Mutations a change that affects a gene on a chromosome Gene mutations change the sequence of nitrogen bases along a DNA strand.  This could change the structure of proteins that a cell makes. Two Types: substitution mutation frameshift mutation.

Substitution Mutation THE DOG BIT THE CAT. THE LOG BIT THE CAT. Changing a single letter changes the meaning of the sentence.  In DNA, changing one nitrogen base could change the code for certain proteins.  Notice that while one word was changed, the other words were not affected.

Frameshift Mutation adding an extra letter to the first sentence  (you must keep all words to 3 letters) : THE SDO GBI TTH ECA T. Notice that when the letter S was added, every letter after that was shifted causing the entire sentence to be altered.   The same effect would also result from the deletion of a single letter.  In DNA, the addition or deletion of a single nitrogen base could have devastating consequence because many more genes and proteins could be affected.

To apply Mendelian genetics to humans, which we will be studying in the next unit, biologists identify an inherited trait controlled by a single gene. The trait must be inherited and not the result of environmental influences. They study how the trait is passed from one generation to the next. OMIM: OMIM HOME tay sachs Map viewer: Homo sapiens

Human Genes The human genome includes tens of thousands of genes. In 2003, the DNA sequence of the human genome was published. In a few cases, biologists were able to identify genes that directly control a single human trait such as blood type.

How Can Karyotype Analysis Detect Genetic Disorders? A karyotype is a picture in which the chromosomes of a cell have been stained so that the banding pattern of the chromosomes is visible. Cells in metaphase of cell division are stained to show distinct parts of the chromosomes. The cells are then photographed through the microscope, and the photograph is enlarged. The chromosomes are cut from the photograph and arranged in pairs according to size, arm length, centromere position, and banding patterns. Karyotypes have become increasingly important to genetic counselors as disorders and diseases have been traced to specific visible abnormalities of the chromosomes.

OMIN - Our Gene Map! Quiz: http://mset.rst2.edu/portfolios/s/saffran_m/thesis/m_quiz.htm

Bellwork: Thurs. Nov. 29, 2012 The purpose of the detergent in the DNA Extraction Experiment was to________________________________ The purpose of the ethyl alcohol in the DNA Extraction Experiment was to________________________________ In the video what does one wrong letter cause?____________________ Cracking the Code of Life “One Wrong Letter”

Bellwork: Tues. Nov. 18, 2010 1. The labeled structure (x) to the right is a ________________ 2. The dotted lines represent __________ _____________ 3. Why are there two in some cases and three in others? ________________________________ 4. What is the difference between a purine and a pyrimidine? _______________________