Freshman Biology Semester Two RA Activity Each table

Freshman Biology Semester Two

� RA Activity: � Each table partner reads one section and takes notes p. 296 -298: �Recessive Genetic Disorders �Dominant Genetic Disorders � Take turns teaching each other about your section while the other partner takes notes! (you should have notes on Recessive and Dominant disorders when finished!) � Read and take notes on pg. 299 -301 �Pedigrees/Analyzing pedigrees �Complete Pedigree Quiz Problem on pg. 300

� Incomplete dominance � Codominance � Multiple alleles � Polygenic traits � Multifactorial traits

� One allele is not completely dominant over the other; heterozygotes show a blending of the trait

� Neither allele is dominant over the other; heterozygotes express both alleles at the same time (not a blending) � Ex: Both black and white feathers in chickens � Ex: Both white and red hairs in roan cattle

� Sickle Cell Anemia is an example of Codominance in human red blood cells. � What is the effect of the disorder? �Sickle � If cells do not transport oxygen efficiently a person has alleles for normal shaped hemoglobin, they will have normal red blood cells. � A person who is homozygous for sickle cell has all sickle shaped red blood cells. � Heterozygous individuals have both types of red blood cells.

� In tulips, yellow color is incompletely dominant to red. Cross a homozygous red (R) tulip with a homozygous yellow (Y) tulip. Determine genotypic and phenotypic ratios of the offspring. �A purple-feathered penguin (P) mates with a green penguin (G). �What are the genotypes and phenotypes of their offspring? �If two of the above offspring mate, what is the phenotypic ratio of their offspring?

� Gene has more than just two alleles possible � Remember- each individual still just has 2 � Ex- rabbit fur color (4 possible alleles)

� Human Blood Types have a gene that displays multiple alleles and codominance � ABO gene has three alleles �IA codes for a A-type ID tag on red blood cells �IB codes for a B-type ID tag on red blood cells �i codes for no ID tag on red blood cells � IA and IB alleles are codominant

� Possible �A Phenotypes and Genotypes blood type (IAIA or IAi) �B blood type (IBIB or IBi) �AB blood type (IAIB) �O blood type (ii)

� More than one gene codes for a trait � Wide range of phenotypes and genotypes possible � Ex- eye color

� Phenotype is a blend between genetic inheritance and environment

� Moms give �Sons and Daughters one of their X chromosomes (random choice) �Eggs have a single X chromosome � Dads give �Daughters their X chromosome �Sons their Y chromosome �Half of the sperm carry an X �Half carry a Y

�A Barr Body is an inactivated X chromosome in a female body (somatic) cell. � Why does this happen? �Males and Females only need one functioning X chromosome in their body cells. �Since females have 2 X chromosomes in all of their body cells, one is inactivated and unused. � Can we see this in organisms? �Calico colored cats have different colored patches of hair, depending on which X chromosome becomes an inactive Barr Body.

� Autosomal Dominant/Recessive �Gene for Trait is found on a autosome �Can be dominant or recessive � Sex-linked �Gene for Trait is found on a sex chromosome �Most (almost all) are found on X (many more genes than Y) �Can be dominant or recessive

� Moms �No “bad” X’s- 0% chance of passing on �One “bad” X- have a 50% of passing the “bad” X to their offspring �Two “bad” X’s- have a 100% chance of passing one of them on � Dads (can only have one copy) �Only Y pass the “bad” X to daughters; sons get the

� Only Males can have them � Dads pass on the trait to all sons

� Genotypes of each parent are written as superscripts on their sex chromosomes �Ex: XHXh and Xh. Y � Remember males only have one copy because they only have one X � DO NOT CROSS TWO FEMALES � When analyzing data �If question asks about offspring, consider all 4 �If question narrows it down to one sex, only look at the two of that sex

� Show up more in males �Females Harder to inherit two “bad” X’s to show disorder �Males have two X’s have only one X They only have to inherit the one copy to show the disorder

�Not all genes independently assort �Only happens with genes on different chromosomes �Genes on the same chromosome are linked (where one goes the others go too) �For example, if One homologous chromosome has alleles A, B, and c for three genes The other homologous chromosome has alleles A, b, and C Then the offspring cannot get A, B, and C or a, b, and c or any other combinations

� Crossing-over can change the combinations of linked genes � The further apart that two genes are on a chromosome, the more likely that they are to cross-over � Gene maps are maps of chromosomes that show the locations of genes and the distances between them

Humans have 23 paired chromosomes in somatic cells � Each chromosome has many genes located on it � Some genes have a simple Mendelian type of inheritance � Most traits have a complex inheritance � �Polygenic traits �Multiple Alleles �Influenced by Both Genetics and Environment

�A karyotype is a picture of chromosomes within a somatic cell � Normal Karyotypes have 46 Chromosomes � Homologous chromosomes are paired � Autosomes (non-sex chromosomes) are arranged from largest to smallest �Largest autosome is #1: smallest autosome is #22 � Sex �XX chromosomes are last (#23) in females �XY in males

� Karyotypes can tell: �Sex of Individual �Presence of a Chromosomal Disorder Extra or missing whole chromosomes Missing piece or extra piece of chromosome � Can’t tell: �Genetic Disorders from Small Mutations

� Missing or extra whole chromosomes or pieces of chromosomes � The condition is determined by which chromosome is affected �This is because each chromosome has different genes � May affect all cells �Fertilized egg or sperm had the mistake � Person may be a mosaic (some normal, some affected cells) �Mistake happened later in development

� Mistake during Meiosis or Mitosis � Non-disjunction: failure of the chromosomes to separate properly �Often happens in Anaphase I when tetrads separate

� Trisomy � 3 copies of one type of chromosome � Monosomy � 1 copy of one type of chromosome �Only monosomy that is viable is XO

� Down’s Syndrome (Trisomy 21) � Edwards Syndrome (Trisomy 18) �Characteristics � Patau Syndrome (Trisomy 13) � Turners Syndrome (XO) � Kleinfelter Syndrome (XXY)

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