What Can Our Chromosomes Tell Us?

What are Chromosomes? What do you see through the microscope lens?

What are Chromosomes?

What are Chromosomes? Compact spools of DNA. “DNA Packages” We have 46 “packages” in each cell 23 from Father 23 from Mother

What do Chromosomes Look Like? Very small Best seen during mitosis

Why do Scientists Look at Chromosomes? Diagnose or predict genetic disorders Prenatal testing Diagnosis can help patients receive medical treatment

How do you Read a Chromosome? Three key features Size Banding Pattern Centromere Position

What are Centromeres for? Required for chromosome separation during cell division. Attached to microtubules Each chromosome has only one centromere. Position helps scientists tell chromosomes apart.

What are Centromeres For? Position of centromere can be describe in three ways: Metacentric = near the center Submetacentric = off-center therefore one arm is longer than the other Acrocentric = resides very near one end

Centromere Positions

What is a Karyotype? Organized profile of a persons chromosomes Chromosomes are arranged by number and size, from largest to smallest

Making a Karyotype Scientists take a picture of someone’s chromosomes Each chromosome is then cut out and matched according to: Size Banding pattern Centromere position

Making a Karyotype

Karyotypes and Genetic Disorders Normal human karyotype 46 chromosomes 22 pairs of autosomes 2 sex cromosomes What happens if….. Too many or too few chromosomes? Missing pieces of chromosomes? Mixed up pieces of chromosomes?

Types of Mutations Deletion Inversion Translocation Nondisjunction Duplication

Deletion Breakage A piece of the chromosome is lost

Inversion Chromosome segment breaks off Segment flips around backwards Segment reattaches

Duplication Occurs when a gene sequence is repeated

Translocation Involves two chromosomes that are not homologous Part of one chromosome is transferred to another chromosome

Nondisjunction Failure of chromosomes to separate during meiosis Causes gamete to have too many or too few chromosomes

Chromosome Mutation Animation

Chromosome Mutations

What Can’t we see in a Karyotoype? Individual DNA strands or genes. The number of genes in any given area of a chromosome. The presence or location of small mutations.

References http://learn.genetics.utah.edu/units/disorders/karyotype http://www.biologyjunction.com/pwpt_biology.htm