Introduction to Genetics- Phenotype SJCHS. Genes Offspring get half of their genes from either...
-
Upload
martina-mccoy -
Category
Documents
-
view
230 -
download
3
Transcript of Introduction to Genetics- Phenotype SJCHS. Genes Offspring get half of their genes from either...
Introduction to Genetics- Phenotype
SJCHS
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
Genes• Offspring get half of their genes from either parent; inheritance
is random• Phenotype: traits of an organism (determined by proteins
produced)•Phenotype depends on type of inheritance
Complete Dominance
2 different kinds of alleles • Dominant allele: Determines
the phenotype• NOT THE MOST
COMMON ALLELE• Wild type: Most common
allele
• Recessive allele: No affect on phenotype if dominant allele present
Incomplete Dominance• Incomplete dominance: the combination of two different alleles in
a heterozygote• Heterozygote still has 2 alleles, not a new or different allele
Example• Snap dragons
• 2 alleles for color: red or white
• If a flower has one of each allele, phenotype will be pink
Example• Human Hair: 2 alleles
• 1 allele for curly hair• 1 allele for straight hair• Heterozygote (1 curly hair allele and 1 straight hair allele)
results in wavy hair
Multiple Alleles• Multiple Alleles: Some genes have more than 2 alleles
• Can have multiple dominant or recessive alleles• Codominant: When two dominant alleles are present, both
phenotypes are equally expressed
Example• In rabbits, there are 4 different alleles that control coat color
• Order of alleles from most dominant to most recessive•Brown, Chinchilla, white with black tips, white
QuickTime™ and a decompressor
are needed to see this picture.
Example• Human blood type is determined by carbohydrates on surface of
cell• 2 dominant alleles code for A carbohydrate, B carbohydrate• Type AB means person has both carbohydrates (and both
dominant alleles)• Type O- no carbohydrates (recessive)
Polygenic• Polygenic: A single trait can be influenced by more than one gene
QuickTime™ and a decompressor
are needed to see this picture. QuickTime™ and a decompressorare needed to see this picture.
Example• Bell Pepper color: Controlled by 3 genes
• Gene 1 controls timing of chlorophyll elimination•Y- early, y normal
• Gene 2 controls coloring of pigments•R- red, r-yellow
• Gene 3 controls amount of pigments•C- normal, c1, c2 less
• Different combinations of alleles result in different colors
QuickTime™ and a decompressor
are needed to see this picture.
Sex Linked Genes
• Sex Linked Genes: Genes located on X or Y chromosome• X linked genetic disorders are more common in males
QuickTime™ and a decompressor
are needed to see this picture.
Example
• Color Blindness• Several X linked genes• 20 times more often in
males
Lethal Genes
• When 2 Lethal genes are inherited, results in an abnormal embryo that does not survive
Example
• Manx gene in cats• Recessive: Normal• Heterozygous dominant: No tail• Homozygous dominant: Abnormal embryo
QuickTime™ and a decompressor
are needed to see this picture.
Environment• “Nature versus Nurture”: Does the environment or genetics
influence certain traits more?• Studies usually use twins or siblings
QuickTime™ and a decompressor
are needed to see this picture.
Behavioral Traits• Is blood type inherited?
• YES
Behavioral Traits• Is risk taking inherited?
• Study of unrelated subjects showed that “novelty seeking” is associated with a particular allele
• Study of twins found no association between “novelty seeking” and having a particular allele
Behavioral Traits• Is musical skill inherited?
• “Absolute Pitch”: The ability to name a note after hearing the sound• Study showed that absolute pitch occurs in more often in people
with certain genetic disorders are more likely to have it• Study showed that those who grew up in East Asia were more
likely to have it• Study showed that professional musicians with early musical
training were more likely to have absolute pitch as opposed to professional musicians without early musical training
Behavioral Traits• Is intelligence inherited?
• Studies show that identical twins not raised by the same family tend to have similar IQs (more so than non-identical siblings raised by the same family)
• Studies have shown that children adopted into families that value education will have increased IQ scores as opposed to children adopted into families that do not value education
Environment
• Some traits not influenced by environment, others are a mix of environment and genetics
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
Epigenetics
• Epigenetics: Study of heritable genetic changes that do not involve DNA; involves gene expression
Epigenetic video
Phenotype
• Inheritance of most traits are complex (a combination of several types of phenotype inheritance)
Example• Human eye color
• Iris- colored part of eye• Made of cells containing a pigment holding organelle (melanosome)• Amount of pigment in melanosomes and number of melanosomes
determine eye color• Pigments act the same as pigments in plants (light that is reflected is the
color we see)
QuickTime™ and a decompressor
are needed to see this picture. QuickTime™ and a decompressor
are needed to see this picture.
Example• Eye color cannot be explained by simple complete dominance• Humans have many eye color genes (polygenic) that produce different
pigments• Order of alleles from most dominant to most recessive
•Brown, Green, Blue•2 allele for blue eyes (multiple alleles)•Genes located different chromosomes
QuickTime™ and a decompressor
are needed to see this picture.
Example• When considering inheritance of eye color, must consider both genes that
control eye color and if parents are heterozygous or homozygous for a trait
QuickTime™ and a decompressor
are needed to see this picture.
Example• Unanswered questions
• Number of genes that control eye color • Amount of pigment produced can change over time (eye color can
change in a person’s lifetime)• Grey, hazel eye color inheritance cannot be explained• Parents with blue eyes can produce offspring with green or brown eyes
QuickTime™ and a decompressor
are needed to see this picture.QuickTime™ and a decompressorare needed to see this picture.