introduction to genetics genetics terms meiosis nondisjunction disorders
TRANSCRIPT
Introduction to Genetics
Genetics Terms
Meiosis
Nondisjunction disorders
Let’s review some genetics terms…
Genetics Terms…
Our body cells are also known as:
A. somatic cells
B. gametes
Genetics Terms…
Our body cells are also known as:
A. somatic cells
B. gametes
Genetics Terms…
Sperm and egg cells are:
A. somatic cells
B. gametes
Genetics Terms…
Sperm and egg cells are:
A. somatic cells
B. gametes
Genetics Terms…
Examples of human somatic cells are:
A. skin cells, bone cells, nerve cells
B. sperm cells, egg cells
Genetics Terms…
Examples of human somatic cells are:
A. skin cells, bone cells, nerve cells
B. sperm cells, egg cells
Genetics Terms…
Somatic cells are diploid, which means…
A. They divide very quickly.
B. They have two sets of chromosomes.
C. They have one set of chromosomes.
Genetics Terms…
Somatic cells are diploid, which means…
A. They divide very quickly.
B. They have two sets of chromosomes.
C. They have one set of chromosomes.
Genetics Terms…
Which of the following is true?
A. Gametes are haploid.
B. Gametes are diploid.
C. Gametes are reproductive cells.
D. Two of the above are true.
Genetics Terms…
Which of the following is true?
A. Gametes are haploid.
B. Gametes are diploid.
C. Gametes are reproductive cells.
D. Two of the above are true.
Genetics Terms…
Which of the following is true?
Homologous chromosomes…
A. are similar in size and shape
B. are found in gametes
C. are found in somatic cells
D. separate during Anaphase II
E. Two of the above are true.
Genetics Terms…
Which of the following is true?
Homologous chromosomes…
A. are similar in size and shape
B. are found in gametes
C. are found in somatic cells
D. separate during Anaphase II
E. Two of the above are true.
Now let’s look at meiosis again…
What kinds of errors can happen during meiosis?
Nondisjunction
• can happen during Anaphase I or during Anaphase II
• results in gametes can have too many or too few chromosomes
• can also happen in mitosis, but this is less harmful because it isn’t passed on to the next generation
Chromosomal Disorders
• can be caused by the wrong number of chromosomes or changes (mutations) in the genetic information carried on chromosomes
Karyotype - male or female?
Karyotype - male or female?
Down syndrome (trisomy 21)
Down Syndrome
• affects about 1 in 800 babies
• varying degrees of intellectual disability
• characteristic facial features
• often have heart defects and other problems
Trisomy 13
Trisomy 18
Trisomy 13 & Trisomy 18
• 1 in 16000 babies are born with trisomy 13 and 1 in 5000 are born with trisomy 18
• severe intellectual disabilities
• many physical birth defects
• most affected babies die before their first birthday
Klinefelter syndrome
Klinefelter syndrome
• affects about 1 in 500-1000 boys
• usually have normal intelligence but many have learning problems
• as adults they produce less than normal amounts of testosterone and are infertile
Turner syndrome
Turner syndrome
• affects 1 in 2500 girls• usually infertile and do not undergo
normal puberty changes unless they are treated with hormones
• some have health problems including heart and kidney defects
• normal intelligence but some have learning difficulties
Triple X
Triple X
• affects 1 in 1000 females
• usually no physical birth defects, experience normal puberty and are fertile
• usually have normal intelligence but many have learning problems
XYY
XYY
• affects 1 in 1000 males
• sometimes taller than average, have normal sexual development and are fertile
• most have normal intelligence, though some have learning, behavioral and speech/language problems