The building blocks of heredity.
Genetics is what makes us unique. There is a shuffling of genes in the making of sperm & eggs. This makes each egg and sperm different from all the rest. Offspring from the same mother and father have the same building blocks but each house (so to speak) is different.
Then when the unique sperm meets a unique egg, there is more matching and mismatching. This process is more systematic, as Mendel showed. But all these connections between parental genetic contributions give us great diversity in our genetic makeup.
Here’s what is included in this lesson:
- Mendel
- dominant-recessive
- autosomal genes
- sex-linked genes
- polygenic traits
Photo
Story
Mind Map
Notes
- Genetics
- Gregor Mendel (1822-1884)
- 1st experimental study genetics
- Took long walks, found unusual ornamental plant
- Planted it next to typical variety
- Grew progeny side by side
- Found
- Offspring show essential traits of parents
- Not influenced by environment
- Each transmits only half its hereditary factors to its offspring
- Different offspring of same parents receive diff set of hereditary factors
- Traits inherited in certain ratios
- Genes dominant or recessive
- Factors are inherited intact
- Humans
- 46 chromosomes
- 23 from each; paired
- 25,000 genes (all together)
- Two copies, 1 from each
- Matching is by chance
- Shuffling
- Unique combination
- Genes affect structures
- No single gene causes any behavior
- Dominant = single copy from either parent carries trait
- Heterozygous = coded differently
- Recessive
- Copy from each parent required
- Can unknowingly carry disease
- Can be hidden for generations
- Affected parent (Dad or Mum)
- All children have equal chance of inheritance
- Dominant-Recessive
- Dominant Wins ¾ Times
- Dominant Dominant
- Dominant Recessive
- Recessive Dominant
- Recessive Recessive
- Mendel’s peas
- smooth or wrinkled
- green or yellow
- short or tall
- Incomplete Recessive
- In some flowers
- Red and white produce pink
- In humans
- Most cases that look incomplete
- Multiple mutations
- Tay-Sachs disease
- 2 different recessive mutations
- Sickle Cell Anemia
- Carriers show no symptoms
- Unless climb mountains (low oxygen)
- Tay-Sachs disease
- Single Traits
- 1. Autosomal Traits
- Not X or Y
- Autosomal = equal in each sex
- Single gene on an autosome (non-sex chromosome)
- Dominant Trait Examples:
- Huntington’s disease
- Neurological disease
- Many copies of gene segment
- Recessive Trait Examples:
- Albinism
- Cystic Fibrosis
- Affected parent (Dad or Mum)
- Children have 50% of inheriting one mutated allele
- Either get yours or spouse’s
- Makes you a carrier
- Carrier
- One mutated allele
- One normal allele
- Allele = gene option (green or yellow)
- Put two carriers together
- 25% chance will transmit mutated gene
- 1 will be unaffected
- 2 will be carriers
- 1 will be affected
- Get 2 bad copies
- 2. Sex-Linked Traits
- Sex-linked = appear in only one sex
- X-Chromosome Linked
- Females
- Inherit X from mother
- Inherit X from father’s mother
- Healthy copy beats unhealthy
- Problems in women only when both copies flawed
- Rare
- Have 1 bad copy = carrier
- Have 2 bad copies = show trait
- Y-Chromosome
- Most genes come in pairs
- Except males
- One Y chromosome
- One X chromosome
- Get X chrom. from mother
- Only one copy
- No backup
- Y-Linked Traits
- Only in men
- Traits passed from father to son
- Few genes on Y chromosome
- Coffin-Lowry Syndrome
- Mutation in ribosomal protein gene
- Mental retardation
- Short stature
- Craniofacial
- Skeleton
- Male Pattern Baldness
- Begins in front, move backward
- M shape, then U-shaped
- Current best gues
- Susceptibility Y-linked; can pass on to son
- Hair structure X-linked
- 3. Sex-limited Traits
- Autosomal traits that are expressed differently in males & females
- Sex-limited = appear in both
- Male & female elephant seals
- 1. Autosomal Traits
- Single Gene Disorders
- 4000+
- Cystic Fibrosis
- Hemophilia
- Sickle cell
- PKU (Phenylketonuria)
- Autosomal Recession
- 100% genetic
- Nonfunctional hepatic enzyme
- Can’t process amino acid (phenylalanine)
- Can lead to
- mental retardation & seizures
- death at young age
- Diet without substances that need enzyme
- 100% environment
- Two factors
- Gene
- Diet
- Polygencic Disorders
- Complex & multifactorial
- Multiple genes in combination
- 10 genes involved in eye color
- Cluster in families
- No clear pattern
- Run in families
- Also lifestyle and environment
- Examples
- Multiple Sclerosis
- Heart disease & hypertension
- Asthma
- Mood disorders
- Cleft palate
- Obesity
- Cancer
Terms
- 25,000 genes
- 46 chromosomes
- affected parent
- albinism
- allele
- asthma
- autosomal traits
- autosome
- canalization = robustness, strongly canalized behaviors develop in many different environments
- cancer
- carrier
- chromosomes = combination of DNA, RNA and protein; human cells have 46 (23 pairs); holds genes
- cluster
- Coffin-Lowry syndrome
- collectivist societies = cultures that value group achievement; opposite of individualism
- cystic fibrosis
- deoxyribonucleic acid (DNA) = molecule of genetic code, double-helix structure
- dominant
- dominant–recessive inheritance = Medelian theory, genes don’t mix, win-lose (freckles, no-freckles)
- environmental influence
- epigenesis = assumes relationship between genetics and environment is bidirectional
- essential traits
- experimental study of genetics
- extended-family household = children parents, grandparents, aunts, uncles; all in one house
- fraternal twins (dizygotic) = two fertilized eggs, different gene combination, same environment
- gametes = reproductive cells (sperm and egg)
- gene = short piece of genetic code (DNA and RNA)
- genes
- genetic counseling = helping patients at risk for inherited disorders to evaluate options
- genetic–environmental correlation = amount both factors contribute to a trait
- genetics
- genomic imprinting = non-Mendelian inheritance, genes are chemically turned on or off
- genotype = genetic composition
- hemophilia
- hepatic enzyme
- hereditary factors
- heritability estimate = how much trait is due to genetics
- heterozygous
- heterozygous = each parent gives different allele (freckles & no-freckles)
- homozygous = each parent gives same allele (freckles gene from each)
- Huntington’s disease
- hypertension
- identical twins (monozygotic) = single fertilized cell divides, each becomes a child
- incomplete dominance = mixing of two traits, each halfway; might not exist in humans
- incomplete recessive
- individualistic societies = cultures that value personal achievement; opposite of collectivism
- inheritance
- kinship studies = compare family characteristics; including identical twin studies
- male pattern baldness
- meiosis = replication of gonad cells, shuffles genes in each chromosome pair, makes 4 gametes with only 23 chromosomes, each is a unique combination of parents” genetic material
- Mendel, Gregor
- Mendel’s peas
- mitosis = cell replication process of making two identical copies
- mood disorders
- multifactorial
- multiple mutations
- multiple sclerosis
- mutation
- niche-picking = tendency to pick activities that match inherited traits
- obesity
- offspring
- phenotype = observation characteristics
- PKU (Phenylketonuria)
- polygencic disorders
- polygenic inheritance = traits based on multiple genes
- prenatal diagnostic methods = testing for diseases and conditions before birth
- progeny
- public policies = governmental programs and laws
- range of reaction = portion of gene-environment interaction due to genetics
- recessive
- sex chromosomes = pair of chromosomes that determine sex of offspring
- sex-limited traits
- sex-linked traits
- shuffling
- Sickle Cell Anemia
- single gene disorders
- single traits
- socioeconomic status (SES) = composite of work experience, education & family wealth
- subculture = cluster within a society, group that differentiates itself from general culture
- Tay-Sachs disease
- X chromosome
- X-linked inheritance = genes on female chromosome, inherit from mother-grandmother
- Y chromosome
- Y-linked inheritance = genes on male chromosome, only a few genes present
- zygote
Quiz
- 1. Who 1st studied genetics experimentally:
- a. Mendel
- b. Erikson
- c. Freud
- d. Galen
- 2. Y-linked traits occur only in:
- a. spring
- b. boys
- c. girls
- d. trick question; boys & girls
- 3. A gene option (green-yellow flowers) is an:
- a. occipita
- b. ablator
- c. ovum
- d. allele
- 4. In humans, most major diseases are:
- a. orthogonal
- b. polygenic
- c. apotosic
- d. Y-linked
- 5. What condition is caused by a single dominant gene:
- a. cystic fibrosis
- b. heart disease
- c. Huntington’s
- d. albinism
Answers
- 1. Who 1st studied genetics experimentally:
- a. Mendel
- b. Erikson
- c. Freud
- d. Galen
- 2. Y-linked traits occur only in:
- a. spring
- b. boys
- c. girls
- d. trick question; boys & girls
- 3. A gene option (green-yellow flowers) is an:
- a. occipita
- b. ablator
- c. ovum
- d. allele
- 4. In humans, most major diseases are:
- a. orthogonal
- b. polygenic
- c. apotosic
- d. Y-linked
- 5. What condition is caused by a single dominant gene:
- a. cystic fibrosis
- b. heart disease
- c. Huntington’s
- d. albinism
Summary
Bonus
Photo credit
Story
Dave, our fictional character, does not exist…yet. When he does, there are a lot of things we are going to want to know about him. All of the following characteristics will be a part of understanding Dave.
Before we get to Dave, let’s discuss development itself. There are five things you should know.
