Pola-pola hereditas - Biologi kelas 12 SMA

Summary

This video script provides an engaging explanation of genetic inheritance patterns and chromosomal disorders. It covers the basics of genetic abnormalities such as Down Syndrome, Edward Syndrome, and Patau Syndrome, detailing the specific chromosomal changes that cause these conditions. Additionally, it explores different sex determination systems across various species, including humans, insects, and other animals. The video also explains how sex is determined in Drosophila melanogaster (fruit flies) using the X to autosome ratio, which differs from human sex determination. The video is informative and encourages viewers to engage with the content.

Takeaways

• 😀 **Down Syndrome (Trisomy 21)**: Down Syndrome is caused by an extra chromosome 21, leading to mental impairment and distinctive physical features.
• 😀 **Edwards Syndrome (Trisomy 18)**: This syndrome involves an extra chromosome 18, causing a smaller head, overlapping fingers, heart defects, and a generally short life expectancy.
• 😀 **Patau Syndrome (Trisomy 13)**: Trisomy 13 leads to physical defects like a small head, cleft lip, extra fingers, and severe brain, heart, and kidney defects, often resulting in early death.
• 😀 **Sex Determination in Humans**: In humans, males have XY chromosomes and females have XX chromosomes. This chromosomal combination dictates biological sex.
• 😀 **X0 System of Sex Determination**: In some insects, males have only one X chromosome (XO), while females have two X chromosomes (XX). This system differs from the XY system seen in humans.
• 😀 **ZW System of Sex Determination**: In some animals like birds and reptiles, the sex is determined by the ZW system, where males are ZZ and females are ZW.
• 😀 **2N System of Sex Determination**: In some insects, such as bees, the number of chromosomes determines sex. Females have a full set (2N), while males have a single set (N).
• 😀 **Drosophila Sex Determination**: The sex of *Drosophila melanogaster* (fruit fly) is determined by the ratio of X chromosomes to autosomes (X/A). A ratio of 0.5 results in a male, while 1 results in a female.
• 😀 **X/A Ratio in Drosophila**: In *Drosophila*, if X/A is greater than 1, the individual is a superfemale, and if X/A is less than 0.5, the individual is a supermale.
• 😀 **Complex Sex Determination in Drosophila**: The ratio of X chromosomes to autosomes can lead to intersex individuals in *Drosophila*, which is a mixture of male and female characteristics.
• 😀 **Understanding Hereditary Patterns**: The video emphasizes understanding genetic disorders and their patterns of inheritance, providing insight into how chromosomal anomalies affect human development and sex determination.

Q & A

What is Down Syndrome and how is it caused?

Down Syndrome, also known as Trisomy 21, is caused by the presence of an extra chromosome on pair 21. Normally, humans have 46 chromosomes, but in Down Syndrome, there are 47 due to the additional chromosome. This leads to developmental delays and intellectual disabilities.

What are the key characteristics of Edwards Syndrome?

Edwards Syndrome, or Trisomy 18, is caused by an extra chromosome on pair 18. It is characterized by microcephaly (a small head), overlapping fingers, heart defects, abnormal chest and limb development, and typically results in a shortened lifespan.

How is Patau Syndrome different from other trisomy disorders?

Patau Syndrome, or Trisomy 13, involves an extra chromosome on pair 13. It presents with microcephaly, cleft lip, extra fingers (polydactyly), and severe abnormalities in the heart, brain, and kidneys. Unlike other trisomy conditions, it generally leads to death shortly after birth due to the severity of the organ malfunctions.

What are the main differences between the XY and ZW sex determination systems?

The XY system, found in humans and many mammals, uses XX for females and XY for males. The ZW system, found in birds and reptiles, is the reverse, with ZZ for males and ZW for females.

What is the XO system of sex determination, and which species use it?

The XO system is used by some insects, such as grasshoppers. In this system, males have only one X chromosome (XO), while females have two X chromosomes (XX). In some cases, the presence of a single X chromosome can determine the male sex.

How does the 2N system of sex determination work in certain insects?

In the 2N system, found in insects like bees, the number of autosomes determines the sex. If an insect has a diploid set of autosomes (2N), it will be female. If it has a haploid set (N), it will be male.

How does sex determination work in Drosophila melanogaster?

In Drosophila melanogaster, sex determination is based on the ratio of X chromosomes to autosomes. The formula X/A determines the sex: if the ratio is 1, the individual is female, if it is 0.5, the individual is male, and values between these numbers can result in intersex conditions.

Why is the X/A ratio important in determining sex in Drosophila?

The X/A ratio in Drosophila is crucial because it helps determine whether an individual will develop as male or female. A ratio of 1 results in a female, while a ratio of 0.5 results in a male. Other values indicate intersex or super-female/male conditions.

What genetic syndrome is caused by a missing X chromosome in humans?

The genetic syndrome caused by a missing X chromosome in humans is Turner Syndrome. This condition occurs in females who only have one X chromosome (45,X), leading to short stature, infertility, and other physical characteristics.

Can the XO system of sex determination be found in animals other than insects?

Yes, the XO system of sex determination is found in certain insects, like grasshoppers and crickets. In this system, males have only one X chromosome, while females have two, and it does not always correlate with the XY system seen in mammals.