Bell Ringer 4/15 Using the laws of codominance, predict the outcome of crossing a blue flower with a yellow flower. BB  Blue YY  Yellow Using the same information, predict the outcome under the rules of incomplete dominance.

Chromosomes and Karyotyes

Genetic Screening An examination of a person’s genetic makeup Can be done in a fetus or a person already born Looks at the DNA sequence or at chromosomes (a bunch of DNA and protein) When doing genetic screening on a fetus, normally an amniocentesis is performed Produces a picture of chromosomes of a fetus (can only diagnose some disorders)

Chromosomes Made of DNA and protein Found in the nucleus of a cell Is chromatin that is coiled up

After DNA copies itself, the chromosome looks like this: When the copies are attached to each other, each one is called a chromatid Prokaryotes have only ONE main circular chromosome, no nucleus

Number of chromosomes in a cell Diploid (2n) - two of each kind of chromosome in a cell One from each parent All body (somatic) cells in animals are diploid Ex: skin, heart, muscle, stomach In humans the diploid number is 46 (2n = 46)

Haploid (n) – one of each kind of chromosome in a cell Only sex cells (gametes) Sperm and egg In humans, the haploid number is 23 (n=23)

Haploid + haploid = diploid Sex cells have to be haploid because they join together to make a new organism Haploid + haploid = diploid Sperm + egg = baby 23 + 23 = 46 =

Abnormal chromosome numbers Nondisjunction When the chromatids fail to separate during formation of gametes This causes the sperm or egg cells to have an incorrect number of chromosomes

Two types of chromosomes Sex chromosomes X or Y Determine if you are: Male (XY) Female (XX) You have one pair of sex chromosomes, known as the 23rd pair Autosomes All other chromosomes 22 pairs in humans (44 total)

Karyotype  picture of chromosomes in a cell Chromosomes are lined up in pairs (numbered 1-22) from longest to shortest 23rd pair (sex chromosomes) are always last Often used for genetic screenings

Male

Female

Trisomy 21 = 3 of Chromosome 21 (Down Syndrome)

Monosomy = 1 chromosome

Karyotyping Links  Karyotyping For each patient, you should have (to turn in): The name of the karyotype Number of chromosomes, XX or XY, any extra or missing chromosomes Ex: 45,XY,-8 The patient’s diagnosis

Chromosomal Study You need:  Partner  Packet  Scissors  Glue Stick Make two karyotypes  Normal (male or female)  Abnormal (male or female)  After putting your karyotype together, research your genetic disorder to answer the questions on the handout. Once your finish  Clean up!!!  Both names on paper  Unit Guide  Finish Blood Type Worksheet  Google Classroom assignment