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Freshman Biology Semester Two.  RA Activity:  Each table partner reads one section and takes notes p.296-298:  Recessive Genetic Disorders  Dominant.

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Presentation on theme: "Freshman Biology Semester Two.  RA Activity:  Each table partner reads one section and takes notes p.296-298:  Recessive Genetic Disorders  Dominant."— Presentation transcript:

1 Freshman Biology Semester Two

2  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

3  Incomplete dominance  Codominance  Multiple alleles  Polygenic traits  Multifactorial traits

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

5  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

6  Sickle Cell Anemia is an example of Codominance in human red blood cells.  What is the effect of the disorder?  Sickle cells do not transport oxygen efficiently  If 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.

7  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?

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

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

10  Possible Phenotypes and Genotypes  A blood type (I A I A or I A i)  B blood type (I B I B or I B i)  AB blood type (I A I B )  O blood type (ii)

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

12  Phenotype is a blend between genetic inheritance and environment

13  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

14  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.

15  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

16  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 pass the “bad” X to daughters; sons get the Y

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

18  Genotypes of each parent are written as superscripts on their sex chromosomes  Ex: X H X h and X h 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


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

21  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

22  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



25  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


27  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 chromosomes are last (#23)  XX in females  XY in males

28  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

29  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

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

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

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





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