Genetics: Big Ideas

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Genetics Big Ideas
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Vocabulary

• genetics-branch of biology that studies heredity.

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• There is enormous variety among living organisms
  in the world. In the context of heredity, the
  focus is on the origin of variation. Difference
  between individuals within the same species, and
  even within the same family, result from the
  recombination of parents genes or mutations of
  genes in reproductive cells.

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• The basis for the diversity of life lies in the
  DNA molecule. Deoxyribonucleic acid (DNA)
  contains the genetic code for each species. This
  molecule contains 4 smaller compounds that mix
  and match to make millions of proteins like the
  letters of our alphabet nix and match to make
  millions of words. The different proteins are
  responsible for the differences among species and
  within the same species. Each protein code is a
  gene (trait). Genes connect to make up the DNA
  molecule (chromosomes). Chromosomes come in pairs
  and thus genes are paired. Each individual gene
  of the pair can have a little different
  information about that trait. These individual
  differences result in dominance, recessiveness,
  and incomplete dominance and are exhibited
  through characteristics of the organism.

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• Analysis of the patterns of genetic traits
  enhances the understanding of genetic diseases
  and allows for predictions to be made by studying
  pedigrees and probability diagrams. Either one or
  many genes determine an inherited trait of an
  individual, and a single gene can influence more
  than one trait. Some traits are inherited and
  others result from interactions with the
  environment, life style choices, and
  environmental influence human characteristics
  that may or may not be passed on to future
  generations.

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• Technological advances have allowed us to better
  understand how heredity and genetics are
  interrelated. As scientists learn more about the
  human genome, we are able to better understand
  how genetic differences affect the human body and
  allow us to make informed choices.

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Essential Questions

• How are genes and alleles related to genotype and
  phenotype?
• What is the relationship between traits and
  heredity?
• How do genes pass information?
• How can there be a variation in genotype and
  phenotype among offspring from the same parents?
• What does probability have to do with genetics?
• What are dominant and recessive traits?
• How is a Punnett square used to determine the
  probability of possible offspring?
• How can environmental factors and lifestyle
  choices affect human characteristics?
• What is a sex linked disorder?
• What is a pedigree chart and how do you interpret
  it?
• How can some medical conditions be genetic?
• What happens when there is codominance or
  incomplete dominance?

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What is a trait?

• Vocabulary
• Trait a distinguishing characteristic.
• heredity-passing on of characteristics from
  parents to offspring.

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Where do traits come from?

• Your parents pass then down through genetic
  traits. Children can receive half of their genes
  from each parent. Each person actually has about
  70,000 pairs of genes. Genes can be dominant or
  recessive.

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Vocabulary

• Gene-segment of DNA coding for a certian trait.

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What do you think dominant or recessive traits
are?

• Dominant means it is the strongest trait, it
  actually masks or covers up the weaker trait.
  Recessive means it is the weaker trait.

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Vocabulary

• dominant trait-this form always appears and is
  represented by a capitol letter.
• recessive trait- this form will not show up if
  paired with a dominant allele. It is represented
  by a lower case letter.

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What traits do you think are dominant / recessive?

• Which hair color do you think is dominant?
• Brown
• Which eye color do you think is dominant?
• Brown
• Which hair color do you think is recessive?
• Light color or red

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Worksheet

• You will each be given a worksheet
• Look at the list of traits listed below.
  Determine which traits you have and put a check
  mark inside the appropriate column. The left
  column indicates dominant traits while the right
  represents recessive traits. Once you have
  completed your list we will collect class data
  and look at similarities or differences.

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• Is it possible for you to have traits that are
  not visible in your parents? (yes, if both
  parents have heterozygous traits (Bb) then there
  is a 25 chance that the recessive trait be
  passed to an offspring. Both parents could have
  the dominant trait but also be carriers for the
  recessive trait.)

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• allele- Available forms of a gene. You get one
  from mom and one from dad for a total of 2 per
  gene. (example for the gene eye color the
  available alleles are brown, blue, red, hazel,
  gray black) Alleles can be either dominant or
  recessive

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Vocabulary

• heterozygous 2 different alleles, aka hybrid.
  Ex Bb
• homozygous Same alleles, aka purebred. Ex
  homozygous dominant BB, homozygous recessive bb

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• genotype- the 2 letters representing which
  alleles are present (BB, Bb, bb)
• phenotype- what the genotype looks like, the
  physical appearance of a gene.(brown)

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Example
B dominant allele (Brown eyes) b recessive
allele (Blue eyes)
Genotype BB Bb bb
Phenotype Brown Eyes Brown Eyes Blue eyes
Description Homozygous Dominant (purebred) Heterozygous (hybrid) Homozygous Recessive (purebred)
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• One more thing
• Lets get some practice.

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Who thought all of this up?

• You find out. Read Chapter 15, section 1 and do
  section review on page 409.
• When you finish Study vocab words for quiz on
  Wednesday

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Who Figured this all out?Gregor Mendel
Born in 1822 in Czechoslovakia. Became a monk at
a monastery in 1843. Taught biology and had
interests in statistics.
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• After returning to the monastery he continued to
  teach and worked in the garden.
• Between 1856 and 1863 he grew and tested over
  28,000 pea plants

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Mendels experiments

• The first thing Mendel did was create a pure
  generation or true-breeding generation.
• After Mendel ensured that his true-breeding
  generation was pure, he then crossed plants
  showing contrasting traits.
• He called the offspring the F1 generation or
  first filial.

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What will happen when pure yellow peas are
crossed with pure green peas?

• All of the offspring were yellow.
• Hybrids the offspring of crosses between
  parents with contrasting traits

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What did Mendel conclude?

• Inheritance is determined by factors passed on
  from one generation to another.
• Mendel knew nothing about chromosomes, genes, or
  DNA. Why?
• These terms hadnt yet been defined.

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What were Mendels factors

• The factors that Mendel mentioned were the
  genes.
• Each gene has different forms called alleles
• Mendels second principle stated that some
  alleles are dominant and some are recessive.

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Mendels second cross

• He allowed the F1 generation to self-pollinate
  thus producing the F2 generation.
• Did the recessive allele completely disappear?
• What happened when he crossed two yellow pea
  hybrid (F1) plants?

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Results

• ¾ of the peas were yellow, ¼ of the peas were
  green.
• During the formation of the sex cells or gametes,
  the alleles separated or segregated to different
  gametes. (pollen and egg)

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Vocabulary

• Probability
• The likelihood of an event occurring. Chance

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Punnett Square

• Developed by Reginald Punnett.
• A diagram used to show the probability of a
  certain trait being passed from one generation to
  another.

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Reading Punnett squares

• Vocab Gamete a reproductive cell (egg or
  sperm). Contain 1 alleles
• Gametes are placed above and to the left of the
  square
• Offspring are placed in the square.
• Capital letters (Y) represent dominant alleles.
• Lower case letters (y) represent recessive
  alleles.

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• Each parent below is heterozygous for brown eyes
• Each parent shows brown eyes because it is a
  dominant trait.
• 75 probability of brown eyes
• 25 probability of blue eyes 

Parent 1 (dad)
B
b
BB Bb
Bb bb
B
Parent 2 (mom)
4 possible offspring
b
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• When you fill in the Punnett square you have a
  probability of
• So it is possible for two brown-eyed parents to
  produce a blued eyed offspring.