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Chapter 3 Review the following terms: phenotype genotype chromosome DNA gene mitosis meiosis gametes crossing over zygote monozygotic twins dizygotic twins. Chapter 3 Review the following terms: sex chromosomes dominant gene recessive gene pleiotropism modifier genes

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Chapter 3

Review the following terms:

  • phenotype

  • genotype

  • chromosome

  • DNA

  • gene

  • mitosis

  • meiosis

  • gametes

  • crossing over

  • zygote

  • monozygotic twins

  • dizygotic twins


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Chapter 3

Review the following terms:

  • sex chromosomes

  • dominant gene

  • recessive gene

  • pleiotropism

  • modifier genes

  • PKU as example of autosomal disease (p. 78)

  • X-linked inheritance

  • mutation

  • polygenic

  • Down syndrome

  • disorders of the sex chromosomes (p. 83)

  • genetic counseling


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Ethical question:

  • We can now treat PKU through diet, so children who would have died in the first year of life can live normal life spans

  • When they reproduce, they will pass on their genetic disease to their offspring

  • What will happen to the population over time?


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PREGNANCY, BIRTH AND LACTATION

PREGNANCY:

Conception:

  • Three trimesters = nine months = prenatal period

    • Healthy vs. at risk pregnancies

    • Importance of intrauterine environment


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Childbirth

  • Stages of childbirth

  • Normal vs. complicated childbirth, mismanagement.

  • Perinatal period:

    • from beginning of labour to 72 hrs. postpartum

  • Breastfeeding:

    • advantages for infant


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PREGNANCY

  • Only a few hundred sperm arrive where egg is, in the Fallopian tube, and surround ovum.

  • Only one (usually) penetrates ovum

  • Stages of uterine development:

    • zygote:

      • 1-14 days

    • embryo:

      • 3-8 weeks

    • fetus:

      • 9-40 weeks


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Beginning of pregnancy

  • Implantation in the endometrium: @ 7 days approximately: blastocyst stage

  • Intrauterine environment very crucial. Critical and sensitive periods

  • Prenatal care essential


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PREGNANCY

  • Prenatal Care Essential:

    • Toxemia:

      • increased blood pressure

      • fluid retention

      • edema

      • can lead to eclampsia (fatal)

    • Gestational Diabetes


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PREGNANCY

  • Natural method of conception can fail

  • Most common reason:

    • STDs in both men and women, which lead to infertility (e.g. blocked Fallopian tubes or vas deferens)

  • Reproductive technology can help infertile couples

  • Most recent dramatic technology:

    • cloning


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PREGNANCY

  • More Established Reproductive Technologies:

    • Artificial Insemination:

      • Introducing sperm into woman’s vagina or uterus by artificial means

        • single woman

        • husband low sperm count

        • husband dead

        • husband infertile: donor sperm


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PREGNANCY

  • More Established Reproductive Technologies (Cont’d):

    • IVF: in vitro fertilization:

      • test tube or Petri dish is used to mix gametes; once dividing, surgically implanted into woman’s uterus

        • can use both parents’ gametes

        • one parent plus donor’s

        • can be implanted in surrogate’s uterus (“rent-a-womb”)


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PREGNANCY

  • Testing the Conceptus for Abnormalities:

    • amniocentesis (11-14 weeks)

    • CVS: chorionic villus sampling (villi) (6-8 weeks)

      • ultrasound (12-16 weeks)

      • fetoscopy

      • blood test


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PREGNANCY

  • TERATOGENS:

    • anything that causes birth defects (teratos = monster)

    • Critical vs. sensitive periods

    • Maternal Diseases:

      • Rubella

      • Toxoplasmosis (cat’s feces, raw meat)

      • CMV

      • AIDS


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Radiation

    • Chemicals:

      • absorbed through lungs or skin

    • High Temperature:

      • hot bath

    • General Environmental Pollution:

      • what we eat, drink, breathe, touch


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PREGNANCY

e.g. phthalates:

  • alter boys’ genitals

    • hypospadias: urethral opening in wrong spot: along the shaft, even scrotum

    • increase in cryptorchidia: undescended testes (more cancer risk)

    • damage to Sertoli cells: decreased sperm production; decreased quality


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PREGNANCY

  • increased allergies

  • premature breast development in girls

  • found in:

    • perfumes

    • nail polish

    • flooring

    • soft plastics

    • paints

    • adhesives

    • IV lines, medical tubes e.g. nasogastric tube


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Drugs:

prescription, e.g. DES, thalidomide

OTC

“recreational”, illegal

caffeine

aspirin, etc.

PREGNANCY

  • TERATOGENS (Cont’d):


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Smoking:

      • nicotine

        • CO:

          • 200 times more affinity to Hgb than oxygen

      • oxygen supply compromised (5% less)

      • decreases sperm motility:

        • lower fertility

      • less progesterone:

        • miscarriages

      • placental problems

      • higher morbidity and mortality

        • from 9/1000 to 33/1000

      • higher rates of cleft palate and hare lip


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Alcohol:

      • FASD (fetal alcohol spectrum disorder)

        • brain abnormalities:

          • learning difficulties

          • ADDH

          • mental retardation, etc.

        • possible damage to eyes, ears, immune system, internal organs, joints, limbs

        • low birth weight

        • increased prematurity, miscarriage and stillbirth risk


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Alcohol:

      • FASD (fetal alcohol spectrum disorder) (Cont’d)

        • growth retardation

        • facial and cranial malformations

        • dose and timing related

        • no safe dose

        • there is no cure for FASD

        • leading cause of preventable mental retardation


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PREGNANCY

  • TERATOGENS (Cont’d):

    All drug effects:

    • Dose Related:

    • Interactions: hard to tell main effects

      • Possible effects:

        • miscarriage

        • stillbirth

        • low birth weight

        • irritability, hard to soothe

        • shorter attention span (learning)

        • tremors

        • digestive difficulties


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Possible effects (cont’d):

      • organ malformation

      • sluggishness

      • future cancers

      • visual impairment

      • skeletal malformation

      • brain development

      • genital abnormalities

      • prematurity


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Possible effects (cont’d):

      • respiratory difficulties

      • illnesses

      • microcephalia

      • heart defects

      • breach births (more C-sections)


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PREGNANCY

  • TERATOGENS (Cont’d):

  • THERE ARE NO TOTALLY SAFE DRUGS!

    • Most vulnerable:

      • brain, CNS

        • learning problems

        • ADHD

    • Most common mechanism:

      • oxygen deprivation


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Maternal stress:

      • acute or chronic (worse)

        • adrenaline, corticosteroids:

          • compromise oxygen supply for infant

      • after birth:

        • digestive problems

        • low birth weight

        • irritability


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PREGNANCY

  • TERATOGENS (Cont’d):

    • Maternal age:

      • no more obstetrical complications (if healthy)

      • increased Down’s syndrome

    • Other effects of these variables:

      • affect maternal-infant interaction

      • abuse

      • neglect

      • rejection


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PREGNANCY

  • Maternal Nutrition:

    • First trimester:

      • usually not an issue – special cases

    • Second trimester:

      • quality

    • Third trimester:

      • quality and quantity

    • Important:

      • Folic acid: prevents neural tube defects (eg. spina bifida)


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PREGNANCY

  • Maternal Nutrition (Cont’d):

    • Infant Optimal Weight:

      • 7½ - 8 lbs. (European stock)

    • Low Birth Weight:

      • 5½ lbs. or 2,500 g

    • Montreal Diet Dispensary, Agnes Higgins:

      • 500 extra daily calories:

        • 1 qt. milk

        • 1 egg

        • 1 orange


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Low Birth Weight

Definition

  • Low Birth Weight:

    • Infant weighs less than 5.5 pounds (2500 g)

  • Premature:

    • Infant is born at less than 38 weeks gestation


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Types of Low Birth Weight Infants

*Low birth weight infants are either:

  • Preterm (born at less than 38 weeks gestation)

  • Small for gestational age (may be born at term)

    OR

  • Preterm & small for gestational age

    *5.8% of births in Canada involve LBW infants (1996)

    *LWB births involve more risk than “normal” births


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Causes of LBW

  • There is no one cause for LBW, but some include:

    • maternal smoking; drinking; drugs

    • maternal diabetes

    • lack of adequate prenatal care

    • poor nutrition

    • infection

    • unknown causes

  • Even healthy mothers with good prenatal care may give birth to a LBW infant (placental problems)


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Risks for the LBW Infant

  • Health

    • heart & lung

    • vision

    • hearing

    • motor problems

    • developmental problems

  • Environmental

    • abuse

    • attachment problems

  • Later Deficits

    • learning difficulties

    • health problems may persist into adulthood

      There is no way to predict which problems, if any an infant

      may have


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Intervention

  • Necessary at birth (resuscitation, drugs, month + hospital stay)

  • Various tests (vision, hearing, developmental) help detect problems

  • Research here at MUN involves assessing LBW infants

    *Note that intervention does not always lead

    to a successful outcome; all infants are

    different


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  • Maternal diet can affect the genes: epigenetics research: how environmental factors (diet, stress, etc.) can change gene function without altering the DNA sequence

  • Genes can predispose toward cancer or diabetes or schizophrenia, but prenatal environment can override this

  • Genes can be turned “on” or “off”, be intensified or dimmed


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The Dutch Hunger Winter Experience (1944) how environmental factors (diet, stress, etc.) can change gene function without altering the DNA sequence

  • 40,000 pregnant women affected

  • 400 calories a day

  • Babies in third trimester gestation (born right after Allied liberation): low birth weight (average 8 oz. less), shorter, smaller head circumference

  • Babies born 3 months after liberation: normal weight

  • Babies conceived 3 months before liberation (first trimester): stillbirth rate doubled

  • Both second and third trimester babies: higher death rate in the first week post-partum


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In adulthood: how environmental factors (diet, stress, etc.) can change gene function without altering the DNA sequence

  • First trimester (conceived 3 months before liberation): twice the rate of CNS defects, i.e. spina bifida and hydrocephalus. Lack of folic acid

    Effects on third generation:

  • Women who were 1st and 2nd trimester babies during the famine had underweight babies despite good nutrition and health


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Maternal Influences in Utero how environmental factors (diet, stress, etc.) can change gene function without altering the DNA sequence

  • Undernutrition: fetus will divert nutrients (blood) to its brain, shortchanging other organs

  • Liver growth can be stunted: high cholesterol in adulthood

  • Also, obesity is more likely in adulthood: appestat programmed to overeat?

  • Maternal stress: cortisol. Fetus has a “counterhormone” that fails if mom undernourished

  • Maternal diabetes: fetus gets high levels of glucose, stress to fetal pancreas leads to diabetes later in life

  • Maternal estrogen: in high levels can lead to breast cancer. Correlated with too high birth weight

  • Low birth weight: prone to heart disease later. Risk of hypertension

    INTRAUTERINE ENVIRONMENT IS EXTREMELY

    IMPORTANT!


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